RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).
Fluorine-containing heterocycles occupy a central position in pharmaceutical, agrochemical, and materials science due to their unique physicochemical properties and broad functional relevance. The pursuit of efficient and sustainable synthetic methodologies has catalyzed the emergence of photochemi...
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Ukrainian Chemistry Journal| _version_ | 1871466209004748800 |
|---|---|
| author | Wzorek, Alicja Ono, Taizo Baecker, Daniel Zhang, Wei Soloshonok, Vadim |
| author_facet | Wzorek, Alicja Ono, Taizo Baecker, Daniel Zhang, Wei Soloshonok, Vadim |
| author_institution_txt_mv | [
{
"author": "Alicja Wzorek",
"institution": "Institute of Chemistry, Jan Kochanowski University in Kielce, Uniwersytecka 7, 25-406 Kielce, Poland"
},
{
"author": "Taizo Ono",
"institution": "National Institute of Advanced Industrial Science and Technology, 463-8560, Nagoya, Japan"
},
{
"author": "Daniel Baecker",
"institution": "Department of Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Straße 2+4, 14195 Berlin, Germany"
},
{
"author": "Wei Zhang",
"institution": "Department of Chemistry, University of Massachusetts Boston, Boston MA 02125, Unites States;"
},
{
"author": "Vadim Soloshonok",
"institution": "University of Basque Country"
}
] |
| author_sort | Wzorek, Alicja |
| baseUrl_str | https://ucj.org.ua/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2026-07-22T08:23:57Z |
| description | Fluorine-containing heterocycles occupy a central position in pharmaceutical, agrochemical, and materials science due to their unique physicochemical properties and broad functional relevance. The pursuit of efficient and sustainable synthetic methodologies has catalyzed the emergence of photochemistry as a compelling alternative to conventional thermal, acid–base, or redox-based approaches. Indeed, many of the transformations highlighted in this review would be unattainable under traditional reaction conditions, underscoring the distinctive reactivity enabled by light-driven processes.
This review surveys key advances over the past decade in the photochemical synthesis of fluorinated heterocyclic compounds. It begins with an overview of fundamental photochemical principles and the most commonly employed photocatalysts. The discussion then proceeds to categorize reactions into unimolecular, bimolecular, and trimolecular classes.  Unimolecular (intramolecular) reactions typically involve the cyclization of strategically designed substrates capable of forming heterocyclic frameworks upon photoactivation. Unimolecular (intramolecular) reactions represent the most prevalent class, wherein two distinct components contribute complementary fragments to construct the target heterocycle. Trimolecular (three-component) photochemical reactions, by contrast, are exceedingly rare due to the inherent mechanistic, kinetic, and spatial constraints associated with three-body interactions under photochemical conditions.
For each transformation discussed, we detail the photocatalyst employed, the irradiation source, reaction conditions, and the specific fluorination pattern introduced. Photochemistry redefines light not merely as an energy source but as a precise and sustainable reagent—unlocking synthetic pathways with elegance, selectivity, and minimal environmental impact.
This work aims to serve as a comprehensive resource for researchers and practitioners seeking to harness photochemical strategies for the synthesis of fluorinated heterocycles, with an emphasis on catalytic efficiency, structural diversity, and ecological responsibility. |
| doi_str_mv | 10.33609/2708-129X.92.2.2026.26-82 |
| first_indexed | 2026-04-09T01:00:16Z |
| format | Article |
| fulltext |
26 ISSN 2708-129X. Укр. хім. журн., 2025
UDC 546.26-162: 541.13:549.21 doi: 10.33609/2708-129X.92.2.2026.26-82
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS
OF FLUORINE-CONTAINING HETEROCYCLES (review).
Alicja Wzorek1, https://orcid.org/0000-0001-9041-7034
Taizo Ono2, https://orcid.org/0009-0002-3268-2344
Daniel Baecker3, https://orcid.org/0000-0002-1963-9838
Wei Zhang4, https://orcid.org/0000-0002-6097-2763
Vadim A. Soloshonok5*, https://orcid.org/0000-0003-0681-4526
1 Institute of Chemistry, Jan Kochanowski University in Kielce,
Uniwersytecka 7, 25-406 Kielce, Poland;
2 National Institute of Advanced Industrial Science and Technology (AIST),
2266-98, Anagahora, Shimoshidami, Moriyama-ku, Nagoya, 463-8560, Japan;
3 Department of Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy,
Freie Universität Berlin, Königin-Luise-Straße 2+4, 14195 Berlin, Germany;
4 Department of Chemistry, University of Massachusetts Boston,
Boston MA 02125, Unites States of Ameriсa;
5 IKERBASQUE, Basque Foundation for Science,
María Díaz de Haro 3, Plaza Bizkaia, 48013 Bilbao, Spain
e-mail: vadimsoloshonok@gmail.com
Abstract:
Fluorine-containing heterocycles occupy a central position in pharmaceutical, agrochemical,
and materials science due to their unique physicochemical properties and broad functional rel-
evance. The pursuit of efficient and sustainable synthetic methodologies has catalyzed the emer-
gence of photochemistry as a compelling alternative to conventional thermal, acid–base, or re-
dox-based approaches. Indeed, many of the transformations highlighted in this review would be
unattainable under traditional reaction conditions, underscoring the distinctive reactivity ena-
bled by light-driven processes.
This review surveys key advances over the past decade in the photochemical synthesis of
fluorinated heterocyclic compounds. It begins with an overview of fundamental photoche
mical principles and the most commonly employed photocatalysts. The discussion then
proceeds to categorize reactions into unimolecular, bimolecular, and trimolecular classes.
Unimolecular (intramolecular) reactions typically involve the cyclization of strategically designed
substrates capable of forming heterocyclic frameworks upon photoactivation. Unimolecular (in-
tramolecular) reactions represent the most prevalent class, wherein two distinct components con-
tribute complementary fragments to construct the target heterocycle. Trimolecular (three-com-
ponent) photochemical reactions, by contrast, are exceedingly rare due to the inherent mechanis-
tic, kinetic, and spatial constraints associated with three-body interactions under photochemical
conditions.
27https://ucj.org.ua
Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
For each transformation discussed, we detail the photocatalyst employed, the irradiation
source, reaction conditions, and the specific fluorination pattern introduced. Photochemistry re-
defines light not merely as an energy source but as a precise and sustainable reagent—unlocking
synthetic pathways with elegance, selectivity, and minimal environmental impact.
This work aims to serve as a comprehensive resource for researchers and practitioners seeking
to harness photochemical strategies for the synthesis of fluorinated heterocycles, with an empha-
sis on catalytic efficiency, structural diversity, and ecological responsibility.
Keywords: Fluorine Chemistry, Heterocycles, Organofluorine Compounds, Photoredox Ca-
talysis, Structural Diversity, Green Chemistry, Sustainable Methodologies, Environmental Impact.
INTRODUCTION.
Photochemistry is the science of chemical
transformation driven by light. At its heart lies
the interaction between photons—primarily in
the ultraviolet and visible regions—and mo
lecules capable of absorbing this energy and
responding through chemical change [1–4].
These light-induced reactions often proceed
via excited electronic states, enabling transfor-
mations that would be improbable or even in-
accessible under standard thermal conditions
[5–7].
Historically, photochemistry traces its line-
age back to early observations by Herschel and
Faraday, who recognized that light was more
than illumination—it could influence matter
[8–11]. However, the field matured signifi-
cantly with the advent of spectroscopy, quan-
tum mechanics, and laser-based technologies,
which allowed scientists to probe and mani
pulate excited-state dynamics with precision.
Pioneers like Porter and Miyaura helped unveil
the molecular choreography underlying these
light-driven processes [12–14].
The foundational concept begins when a
molecule absorbs a photon, shifting from its
ground electronic state to an excited state. This
higher-energy configuration can initiate a va-
riety of pathways: bond formation or cleavage,
electron transfer, energy migration, isomeriza-
tion, or radical generation. These reactions are
typically non-thermal, unfolding not through
vibrational excitation but via electronic transi-
tions [15–17].
A molecule’s ability to absorb light depends
on the availability of suitable electronic transi-
tions, such as π→π* or n→π*, governed by the
Beer–Lambert law [18–20]. The excited states
accessed—singlet (S₁) or triplet (T₁)—car-
ry distinct chemical potentials and lifetimes,
shaping their reactivity. Processes like inter-
system crossing and internal conversion dic-
tate whether the molecule reacts chemically or
returns to the ground state via photophysical
emission. The quantum yield (Φ) quantifies
the efficiency of these photochemical events,
indicating how many molecular transforma-
tions occur per photon absorbed [21–23].
A crucial distinction exists between photo-
chemistry and photophysics: photochemistry
results in permanent chemical change, while
photophysics involves energy release without
altering molecular structure, as seen in fluo-
rescence and phosphorescence [24].
Photochemistry permeates numerous disci-
plines. In organic synthesis, it enables selective
reactions such as [2+2] cycloadditions, oxida-
tions, and rearrangements [25–27]. In materials
28 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
science, photochemical processes underpin
technologies like photoresists, light-curable
polymers, and organic light emitting diode
(OLED) displays [28–31]. In biochemistry,
light governs critical pathways including pho-
tosynthesis, visual perception, and DNA da
mage and repair [32]. Environmental chemis-
try harnesses solar light to degrade pollutants
and activate photocatalysts, providing green
solutions to industrial waste [33–35].
In essence, photochemistry offers more
than just reactivity—it provides a lens through
which light becomes a tool of molecular design,
capable of unlocking pathways shaped not by
heat, but by photons sculpting the structure
and destiny of chemical species. Photoche
mistry has become a cornerstone of modern
organic synthesis, offering reactivity pathways
that are often inaccessible or impractical under
conventional thermal conditions. By harness-
ing the energy of light—typically in the ultra
violet or visible spectrum—chemists can induce
transformations at ambient temperatures, often
without the need for harsh reagents or elevated
pressures [36–39].
One of the most striking advantages of pho-
tochemical reactions is their ability to activate
specific molecular orbitals through electronic
excitation, enabling reactions like cycloaddi-
tions, radical-mediated rearrangements, and
selective isomerizations. These processes are
not only thermally forbidden but can also pro-
ceed with remarkable selectivity and efficiency
when triggered by light [40–42].
Photochemical synthesis also aligns closely
with green chemistry principles. Light acts as
a reagent with zero chemical waste, and many
photochemical reactions proceed in mild con-
ditions—room temperature, benign solvents,
and low energy input. This dramatically re-
duces the environmental footprint of chemical
manufacturing. Furthermore, advancements
in flow photochemistry have enabled conti
nuous processing with LED-driven reactors,
making these methods scalable and industrial-
ly viable [43–46].
The strategic value of photochemistry in
synthesis lies in its precision and adaptability.
Light intensity, wavelength, and catalyst design
offer programmable control over reaction out-
comes. As the field continues to evolve, photo-
chemical methods are finding growing appli-
cations in pharmaceutical development, fluo
rinated compound synthesis, and eco-friendly
manufacturing.
Building on our expertise in modern phar-
maceutical development [47–52], with a par-
ticular focus on fluorine-containing thera-
peutics [53–61] and compounds derived from
tailor-made amino acids [62–67], we active-
ly pursue and evaluate innovative synthetic
methodologies [68–74]. This strategic direc-
tion is reinforced by the fact that heterocyclic
scaffolds and amino acid derivatives underpin
approximately 85% and 35% of approved phar-
maceutical agents, respectively. Accordingly,
we prioritize advancements in these key syn-
thetic domains [75–88]. Among them, heter-
ocyclic compounds are especially vital in me-
dicinal chemistry, owing to their remarkable
biological activity and structural adaptability,
which render them indispensable tools in ra-
tional drug design [89–92].
Recently, we provided a comprehensive
overview of recent progress in the synthesis
of fluorinated heterocyclic compounds, em-
phasizing emerging strategies such as carbon
nanotube-mediated catalysis [93], the applica-
tion of mechanochemical principles [94], and
the integration of electrochemical methodolo-
29https://ucj.org.ua
Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
gies [95]. In the present review, we build upon
this foundation by advancing the discussion to-
ward environmentally conscious and sustain-
able synthetic practices, with a detailed focus
on photochemical approaches for constructing
fluorinated heterocyclic scaffolds. Photoche
mistry continues to gain recognition as a dy-
namic and strategically valuable research area
with considerable synthetic potential. In this
review, we provide a systematic overview of
studies published over the past decade con-
cerning the photochemical synthesis of fluo-
rine-containing heterocyclic compounds. The
discussion is structured according to the num-
ber of reacting species, encompassing unimo-
lecular, bimolecular, and trimolecular trans-
formations. We anticipate that this compilation
will serve not only as a practical reference but
also as a source of inspiration for researchers
and practitioners in synthetic and medicinal
chemistry, particularly those pursuing envi-
ronmentally sustainable methodologies.
Common transition metal photocatalysts.
Catalysis plays a central role in expanding
the versatility of photochemical transforma-
tions. Photoredox catalysis, which uses visible
light to toggle redox states via transition metal
complexes or organic dyes, allows for a range
of bond-forming reactions, including C–C,
C–N, and C–O couplings. Dual catalysis stra
tegies further integrate light with organocata
lysis or transition metals to enable asymmetric
synthesis, site-selective functionalizations, and
late-stage modifications [96].
Most commonly used transition metal ca
talysts are presented in Fig. 1. Ru(bpy)₃²⁺, or
tris(2,2′-bipyridine)ruthenium(II), is a well-
established photoredox catalyst widely used
in synthetic chemistry. It absorbs visible light
(around 450 nm) and reaches a long-lived ex-
cited state (~1 microsecond), enabling vari-
ous single-electron transfer (SET) and energy
transfer reactions. In its excited state, it acts
as both a strong reductant and a strong oxi-
dant, which allows it to drive a broad range of
transformations. The complex is stable under
air and moisture, operates under mild con-
ditions, and facilitates C–C and C–X bond
formation, dehalogenations, cycloadditions,
and redox-neutral reactions. Its photochemi-
cal behavior aligns well with green chemistry
goals: minimal energy input, reduced waste,
and compatibility with flow systems. It is also
explored for biological applications like pho-
to-induced generation of reactive oxygen spe-
cies (ROS) and targeted therapies. Ru(bpy)₃²⁺
remains a cornerstone in both academic and
industrial photochemistry thanks to its versa-
tility, robustness, and responsiveness to visible
light [97].
Ir(bpy)₃(dtbbpy)⁺ is a heteroleptic iridi-
um(III) polypyridyl complex used as a versa-
tile photocatalyst in visible-light-promoted
reactions. It consists of three bipyridine-type
ligands, including dtbbpy (4,4’-di-tert-butyl-
2,2’-bipyridine), which contributes to en-
hanced solubility and steric protection. Iridi-
um is in the +3 oxidation state, and the com-
plex carries an overall +1 charge. Upon irra-
diation with visible light, the complex enters
a long-lived triplet metal-to-ligand charge
transfer (MLCT) excited state, capable of en-
gaging in single-electron transfer and energy
transfer mechanisms. In its excited state, it acts
as both a strong oxidant (around +1.21 V vs.
SCE) and reductant (about –0.89 V vs. SCE),
making it suitable for both oxidative and re-
ductive photoredox cycles. Ir(bpy)₃(dtbbpy)⁺
has been successfully applied in reactions such
30 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
as radical acylation, decarboxylative couplings,
and C(sp³)–H functionalization in dual cata-
lytic systems (e.g., Ir/Ni). It is also explored in
tandem photoredox cycles involving IrH⁺ and
IrH₃ intermediates, expanding its utility in
multi-electron redox transformations [98].
The complex Ir[dF(CF₃)bpy]₂(dtbbpy)⁺ is a
highly efficient iridium(III) photocatalyst wide-
ly used in visible-light photoredox chemistry.
It features two cyclometalated ligands—3,5-
difluoro-2-(trifluoromethyl)pyridyl-phenyl
(dF(CF₃)ppy)—and one ancillary ligand,
4,4’-di-tert-butyl-2,2’-bipyridine (dtbbpy),
which enhances solubility and steric stability.
This catalyst absorbs light around 380–450 nm
and enters a long-lived triplet MLCT (me
tal-to-ligand charge transfer) excited state. In
this state, it acts as both a strong oxidant (ex-
cited-state potential ≈ +1.21 V vs. SCE) and a
competent reductant (≈ –0.89 V vs. SCE), mak-
ing it suitable for both oxidative and reductive
quenching cycles. Ir[dF(CF₃)bpy]₂(dtbbpy)⁺
is particularly effective in radical acylation
reactions, decarboxylative couplings, and tan-
dem photoredox cycles. It can form reactive
intermediates like IrH⁺ and IrH₃ under mul-
tiphoton conditions, enabling sequential redox
events. These properties make it valuable for
constructing ketones, arylated products, and
complex heterocycles under mild, sustainable
conditions [99].
Ir(dFppy)₃, or tris(2-(2,4-difluorophenyl)
pyridine)iridium(III), is a homoleptic cyclo-
metalated iridium complex widely used in vis-
ible-light photocatalysis. It features three fluo
rinated phenylpyridine ligands, which enhance
its photophysical properties by increasing the
triplet state energy and blue-shifting its emis-
sion. This complex is air- and moisture-stable,
absorbs light around 450 nm, and has a high
triplet state energy (~60 kcal/mol), making it
particularly effective for energy transfer re-
actions. Its excited-state redox potentials are
relatively modest compared to other iridium
complexes, which helps avoid undesired redox
side reactions and makes it ideal for substrates
sensitive to oxidation or reduction. Ir(dFppy)₃
is commonly used in [2+2] photocycloaddi-
tions, E/Z alkene isomerizations, and other
transformations that rely on selective energy
transfer rather than single-electron transfer.
It has also been employed in synergistic dual
photocatalyst systems, where it complements
more redox-active catalysts by handling energy
transfer steps. Overall, Ir(dFppy)₃ is a robust
and selective photocatalyst, especially valuable
in reactions requiring high triplet energy and
minimal redox interference [100].
Finally, (Cp*RhCl₂)₂, or pentamethylcyclo-
pentadienyl rhodium(III) dichloride dimer, is a
robust organometallic complex that has found
increasing utility in photocatalysis, particularly
in visible-light-driven transformations. While
it is more traditionally known for thermal C–H
activation chemistry, recent studies have ex-
plored its photochemical behavior and catalytic
potential under light irradiation. This complex
features two Rh(III) centers bridged by chlo-
ride ligands and stabilized by Cp* (η⁵-C₅Me₅)
rings. It is air-stable, red in color, and solu-
ble in organic solvents like dichloromethane
and chloroform. Upon photoexcitation, it can
participate in ligand-to-metal charge transfer
(LMCT) and engage in catalytic cycles involv-
ing single-electron transfer or energy transfer,
depending on the reaction conditions and sub-
strates. (Cp*RhCl₂)₂ has been used in mecha
nochemical and photochemical C–H bond
functionalizations, halogenations, and annula-
tion reactions. It can also be activated by silver
31https://ucj.org.ua
Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
salts to form cationic Rh(III) species that are
more reactive under light. In some systems, it
has been incorporated into conjugated poly-
mers or heterogenized frameworks to facilitate
CO₂ photoreduction and other light-driven
processes. Its versatility, stability, and compati-
bility with sustainable activation methods such
as blue-light irradiation and electrocatalysis
make it a promising candidate for expanding the
scope of rhodium-based photocatalysis [101].
chemistry, recent studies have explored its photochemical behavior and catalytic potential under
light irradiation. This complex features two Rh(III) centers bridged by chloride ligands and
stabilized by Cp* (η⁵-C₅Me₅) rings. It is air-stable, red in color, and soluble in organic solvents like
dichloromethane and chloroform. Upon photoexcitation, it can participate in ligand-to-metal charge
transfer (LMCT) and engage in catalytic cycles involving single-electron transfer or energy transfer,
depending on the reaction conditions and substrates. (Cp*RhCl₂)₂ has been used in
mechanochemical and photochemical C–H bond functionalizations, halogenations, and annulation
reactions. It can also be activated by silver salts to form cationic Rh(III) species that are more
reactive under light. In some systems, it has been incorporated into conjugated polymers or
heterogenized frameworks to facilitate CO₂ photoreduction and other light-driven processes. Its
versatility, stability, and compatibility with sustainable activation methods such as blue-light
irradiation and electrocatalysis make it a promising candidate for expanding the scope of rhodium-
based photocatalysis [101].
Fig. 1. Common Ru, Ir and Rh photocatalysts.
For these photocatalysts, the most commonly used counterions include PF₆⁻ (hexafluorophosphate),
which is widely favored due to its low coordinating ability and excellent solubility in organic
solvents. Chloride (Cl⁻) is often found in commercially available salts such as
tris(bipyridine)ruthenium(II) chloride. BF₄⁻ (tetrafluoroborate) offers a good balance of solubility
and stability and is also commonly used. ClO₄⁻ (perchlorate) appears occasionally, although less
frequently because of safety concerns. The choice of anion can influence key factors such as
solubility, photophysical properties, and compatibility with different reaction environments. For
photoredox catalysis in organic solvents, PF₆⁻ and BF₄⁻ are especially preferred due to their inert
character and solvent compatibility. Additionally, these photocatalysts align well with the principles
of green chemistry. They operate under mild conditions using visible light, support redox-neutral
pathways, and are compatible with sustainable media, including aqueous-organic systems and flow
chemistry setups. Their combination of chemical reactivity, operational stability, and environmental
friendliness makes them valuable tools for advanced photochemical synthesis [102-104].
Unimolecular reactions.
Most of the unimolecular reactions discussed in this section involve photocatalytic cyclization.
These transformations typically exhibit broad functional group tolerance across the starting
materials, yet demonstrate limited generality with respect to the structural arrangement of reactive
Fig. 1. Common Ru, Ir and Rh photocatalysts.
For these photocatalysts, the most com-
monly used counterions include PF₆⁻ (hexa
fluorophosphate), which is widely favored due
to its low coordinating ability and excellent
solubility in organic solvents. Chloride (Cl⁻)
is often found in commercially available salts
such as tris(bipyridine)ruthenium(II) chloride.
BF₄⁻ (tetrafluoroborate) offers a good balance
of solubility and stability and is also commonly
used. ClO₄⁻ (perchlorate) appears occasionally,
although less frequently because of safety con-
cerns. The choice of anion can influence key
factors such as solubility, photophysical pro
perties, and compatibility with different reac-
tion environments. For photoredox catalysis in
organic solvents, PF₆⁻ and BF₄⁻ are especially
preferred due to their inert character and sol-
vent compatibility. Additionally, these photo-
catalysts align well with the principles of green
chemistry. They operate under mild conditions
using visible light, support redox-neutral path-
ways, and are compatible with sustainable me-
dia, including aqueous-organic systems and
flow chemistry setups. Their combination of
chemical reactivity, operational stability, and
environmental friendliness makes them valu-
able tools for advanced photochemical synthe-
sis [102-104].
Unimolecular reactions.
Most of the unimolecular reactions discussed
in this section involve photocatalytic cyclization.
These transformations typically exhibit broad
functional group tolerance across the starting
materials, yet demonstrate limited generality
with respect to the structural arrangement of
reactive fragments. Successful cyclization re-
quires precise geometric alignment of those
32 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
fragments, making structural predisposition a
key determinant of reactivity.
Zhou et al. (Scheme 1) [105] reported a
highly efficient cyclization protocol (yielding
up to 90%) for the transformation of com-
pounds 1—synthesized from α-bromo acids
and corresponding anilines or phenols—into
fluorinated heterocycles 2. Depending on the
heteroatom (X), the products were identi-
fied as either (Z)-benzo[b]oxepin-2(3H)-ones
(X = O) or (Z)-1H-benzo[b]azepin-2(3H)-ones
(X = N-Alk). The reactions were carried out in
dichloromethane (DCM) under an argon at-
mosphere at ambient temperature, with 2,6-luti-
dine (1.5 equiv.) as the base. Photochemical ac-
tivation was achieved using LED irradiation in
the presence of fac-Ir(ppy)₃ as the photocatalyst.
The radical cyclization proceeded with remark-
able regioselectivity, as no detectable byprod-
ucts were observed. This method enables the
synthesis of heterocycles 2 bearing up to three
fluorine atoms—one on the benzene moiety and
up to two aliphatic fluorines positioned α to the
carbonyl group on the seven-membered ring.
Scheme 1. Synthesis of fluorinated benzoxepines and benzazepines.
fragments. Successful cyclization requires precise geometric alignment of those fragments, making
structural predisposition a key determinant of reactivity.
Zhou et al. (Scheme 1) [105] reported a highly efficient cyclization protocol (yielding up to 90%)
for the transformation of compounds 1—synthesized from α-bromo acids and corresponding
anilines or phenols—into fluorinated heterocycles 2. Depending on the heteroatom (X), the products
were identified as either (Z)-benzo[b]oxepin-2(3H)-ones (X = O) or (Z)-1H-benzo[b]azepin-2(3H)-
ones (X = N-Alk). The reactions were carried out in dichloromethane (DCM) under an argon
atmosphere at ambient temperature, with 2,6-lutidine (1.5 equiv.) as the base. Photochemical
activation was achieved using LED irradiation in the presence of fac-Ir(ppy)₃ as the photocatalyst.
The radical cyclization proceeded with remarkable regioselectivity, as no detectable byproducts
were observed. This method enables the synthesis of heterocycles 2 bearing up to three fluorine
atoms—one on the benzene moiety and up to two aliphatic fluorines positioned α to the carbonyl
group on the seven-membered ring.
Scheme 1. Synthesis of fluorinated benzoxepines and benzazepines.
Li et al. (Scheme 2) [106] described the synthesis of fluorinated benzimidazoles 4 via cyclization of
fluorine-containing N-phenylamidoxime esters 3. The yields of the desired products 4 ranged from
20% to 77%. Reactions were carried out in methyl tert-butyl ether (MTBE) under an argon
atmosphere at ambient temperature. Photochemical activation was achieved using 13 W white
LEDs in the presence of Ir[dF(CF₃)ppy]₂(dtbbpy)PF₆ as the photocatalyst. The process was
relatively slow, with optimal yields obtained after 36 hours of irradiation. Interestingly, the para-
CF₃-benzoic acid moiety on the starting amidoxime esters 3 acted as a sacrificial unit, facilitating
the initiation of the radical chain process.
Scheme 2. Preparation of fluorinated benzimidazoles.
Fluorinated quinolinones and derivatives exhibit a wide spectrum of biological activities, making
them valuable scaffolds in medicinal chemistry. Their bioactivity is largely attributed to the
quinolinone core’s ability to interact with diverse biological targets, and fluorine substitution
enhances pharmacokinetic properties such as lipophilicity, metabolic stability, and membrane
permeability [107-109].
fragments. Successful cyclization requires precise geometric alignment of those fragments, making
structural predisposition a key determinant of reactivity.
Zhou et al. (Scheme 1) [105] reported a highly efficient cyclization protocol (yielding up to 90%)
for the transformation of compounds 1—synthesized from α-bromo acids and corresponding
anilines or phenols—into fluorinated heterocycles 2. Depending on the heteroatom (X), the products
were identified as either (Z)-benzo[b]oxepin-2(3H)-ones (X = O) or (Z)-1H-benzo[b]azepin-2(3H)-
ones (X = N-Alk). The reactions were carried out in dichloromethane (DCM) under an argon
atmosphere at ambient temperature, with 2,6-lutidine (1.5 equiv.) as the base. Photochemical
activation was achieved using LED irradiation in the presence of fac-Ir(ppy)₃ as the photocatalyst.
The radical cyclization proceeded with remarkable regioselectivity, as no detectable byproducts
were observed. This method enables the synthesis of heterocycles 2 bearing up to three fluorine
atoms—one on the benzene moiety and up to two aliphatic fluorines positioned α to the carbonyl
group on the seven-membered ring.
Scheme 1. Synthesis of fluorinated benzoxepines and benzazepines.
Li et al. (Scheme 2) [106] described the synthesis of fluorinated benzimidazoles 4 via cyclization of
fluorine-containing N-phenylamidoxime esters 3. The yields of the desired products 4 ranged from
20% to 77%. Reactions were carried out in methyl tert-butyl ether (MTBE) under an argon
atmosphere at ambient temperature. Photochemical activation was achieved using 13 W white
LEDs in the presence of Ir[dF(CF₃)ppy]₂(dtbbpy)PF₆ as the photocatalyst. The process was
relatively slow, with optimal yields obtained after 36 hours of irradiation. Interestingly, the para-
CF₃-benzoic acid moiety on the starting amidoxime esters 3 acted as a sacrificial unit, facilitating
the initiation of the radical chain process.
Scheme 2. Preparation of fluorinated benzimidazoles.
Fluorinated quinolinones and derivatives exhibit a wide spectrum of biological activities, making
them valuable scaffolds in medicinal chemistry. Their bioactivity is largely attributed to the
quinolinone core’s ability to interact with diverse biological targets, and fluorine substitution
enhances pharmacokinetic properties such as lipophilicity, metabolic stability, and membrane
permeability [107-109].
Li et al. (Scheme 2) [106] described the
synthesis of fluorinated benzimidazoles 4 via
cyclization of fluorine-containing N-phenyla-
midoxime esters 3. The yields of the desired
products 4 ranged from 20% to 77%. Reactions
were carried out in methyl tert-butyl ether
(MTBE) under an argon atmosphere at am-
bient temperature. Photochemical activation
was achieved using 13 W white LEDs in the
presence of Ir[dF(CF₃)ppy]₂(dtbbpy)PF₆ as the
photocatalyst. The process was relatively slow,
with optimal yields obtained after 36 hours of
irradiation. Interestingly, the para-CF₃-benzo-
ic acid moiety on the starting amidoxime es-
ters 3 acted as a sacrificial unit, facilitating the
initiation of the radical chain process.
Scheme 2. Preparation of fluorinated benzimidazoles.
33https://ucj.org.ua
Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
Fluorinated quinolinones and derivatives
exhibit a wide spectrum of biological activities,
making them valuable scaffolds in medicinal
chemistry. Their bioactivity is largely attribu
ted to the quinolinone core’s ability to interact
with diverse biological targets, and fluorine
substitution enhances pharmacokinetic pro
perties such as lipophilicity, metabolic stability,
and membrane permeability [107-109].
González‐Muñoz et al. (Scheme 3) [110] de-
veloped a photochemical protocol for the syn-
thesis of trifluoromethyl-substituted tetrahy-
droquinolines 6 via intramolecular cyclization
of aniline derivatives 5. These precursors fea-
ture an iodine atom and an N-unsaturated moi-
ety, enabling the formation of a six-membered
heterocycle. The reactions were performed
in acetonitrile at ambient temperature, using
2.5 equivalents of Hünig’s base [111] under an
inert atmosphere. Photochemical activation
was achieved with 13 W white LEDs (visible
light) in the presence of Ir(ppy)₃ as the photo-
catalyst. Cyclization proceeded efficiently, with
completion times under 24 hours, affording
the target tetrahydroquinolines 6 in moderate
to good yields ranging from 40% to 80%.
Scheme 3. Synthesis of trifluoromethyl-containing tetrahydroquinolines.
González‐Muñoz et al. (Scheme 3) [110] developed a photochemical protocol for the synthesis of
trifluoromethyl-substituted tetrahydroquinolines 6 via intramolecular cyclization of aniline
derivatives 5. These precursors feature an iodine atom and an N-unsaturated moiety, enabling the
formation of a six-membered heterocycle. The reactions were performed in acetonitrile at ambient
temperature, using 2.5 equivalents of Hünig’s base [111] under an inert atmosphere. Photochemical
activation was achieved with 13 W white LEDs (visible light) in the presence of Ir(ppy)₃ as the
photocatalyst. Cyclization proceeded efficiently, with completion times under 24 hours, affording
the target tetrahydroquinolines 6 in moderate to good yields ranging from 40% to 80%.
Scheme 3. Synthesis of trifluoromethyl-containing tetrahydroquinolines.
Fluorinated cinnamic acid derivatives are widely employed as electrophilic partners in Michael
addition reactions, owing to their enhanced reactivity and utility as convenient building blocks for
introducing aromatic fluorine into structurally complex, biologically active molecules [112–114].
Jovanovic et al. (Scheme 4) [115] reported a photochemical cyclization of enallenylamides 7,
derived from trifluoromethyl-substituted cinnamic acids, to afford sterically constrained bicyclic
dihydropyridinones 8 in yields ranging from 40% to 88%. The transformation proceeds via a [2+2]
cycloaddition pathway, catalyzed by Ir(ppy)₃ (1 mol%) under blue LED irradiation in
dichloromethane at ambient temperature over 18 hours. The nitrogen substituent in the starting
enallenylamides 7 can be an alkyl group or a hydrolyzable acyl or Boc moiety, allowing for facile
deprotection and access to NH-functionalized products. This structural versatility broadens the
scope of potential biological applications for the resulting dihydropyridinones.
Scheme 4. Synthesis of trifluoromethyl-containing dihydropyridinones.
Gore and Wang (Scheme 5) [116] reported a series of intramolecular cascade reactions that enable
the synthesis of dihydroisochromenes 10 as central scaffolds within complex polycyclic
architectures. These structures feature a bridged framework comprising six-, five-, and three-
membered aliphatic rings fused to an aromatic system. The starting materials—fluorinated (E)-1-
phenyl-3-[2-((E)-styryl)phenyl]prop-2-en-1-ones 9—were subjected to visible-light irradiation (blue
LEDs) in the presence of Ir[dF(CF₃)ppy]₂(dtbbpy)PF₆ as the photocatalyst in DMSO at ambient
temperature. The reactions proceeded efficiently over 7 hours, affording the polycyclic products 10
in excellent yields ranging from 65% to 93%. Mechanistic studies suggest that the transformation
Fluorinated cinnamic acid derivatives are
widely employed as electrophilic partners in
Michael addition reactions, owing to their
enhanced reactivity and utility as convenient
building blocks for introducing aromatic flu-
orine into structurally complex, biologically
active molecules [112–114]. Jovanovic et al.
(Scheme 4) [115] reported a photochemical
cyclization of enallenylamides 7, derived from
trifluoromethyl-substituted cinnamic acids, to
afford sterically constrained bicyclic dihydro-
pyridinones 8 in yields ranging from 40% to
88%. The transformation proceeds via a [2+2]
cycloaddition pathway, catalyzed by Ir(ppy)₃
(1 mol%) under blue LED irradiation in di-
chloromethane at ambient temperature over
18 hours. The nitrogen substituent in the start-
ing enallenylamides 7 can be an alkyl group
or a hydrolyzable acyl or Boc moiety, allowing
for facile deprotection and access to NH-func-
tionalized products. This structural versatil-
ity broadens the scope of potential biological
applications for the resulting dihydropyridi-
nones.
Gore and Wang (Scheme 5) [116] reported a
series of intramolecular cascade reactions that
enable the synthesis of dihydroisochromenes
10 as central scaffolds within complex poly-
cyclic architectures. These structures feature
a bridged framework comprising six-, five-,
and three-membered aliphatic rings fused to
an aromatic system. The starting materials—
fluorinated (E)-1-phenyl-3-[2-((E)-styryl)
phenyl]prop-2-en-1-ones 9—were subjected
to visible-light irradiation (blue LEDs) in the
presence of Ir[dF(CF₃)ppy]₂(dtbbpy)PF₆ as
34 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
the photocatalyst in DMSO at ambient tem-
perature. The reactions proceeded efficiently
over 7 hours, affording the polycyclic prod-
ucts 10 in excellent yields ranging from 65%
to 93%. Mechanistic studies suggest that the
transformation operates via an energy-trans-
fer pathway, offering high selectivity and broad
substrate tolerance. Notably, the methodology
accommodates various fluorine substitutions
on the aromatic ring, expanding its utility for
the synthesis of structurally intricate, fluo
rinated frameworks with potential biological
relevance.
González‐Muñoz et al. (Scheme 3) [110] developed a photochemical protocol for the synthesis of
trifluoromethyl-substituted tetrahydroquinolines 6 via intramolecular cyclization of aniline
derivatives 5. These precursors feature an iodine atom and an N-unsaturated moiety, enabling the
formation of a six-membered heterocycle. The reactions were performed in acetonitrile at ambient
temperature, using 2.5 equivalents of Hünig’s base [111] under an inert atmosphere. Photochemical
activation was achieved with 13 W white LEDs (visible light) in the presence of Ir(ppy)₃ as the
photocatalyst. Cyclization proceeded efficiently, with completion times under 24 hours, affording
the target tetrahydroquinolines 6 in moderate to good yields ranging from 40% to 80%.
Scheme 3. Synthesis of trifluoromethyl-containing tetrahydroquinolines.
Fluorinated cinnamic acid derivatives are widely employed as electrophilic partners in Michael
addition reactions, owing to their enhanced reactivity and utility as convenient building blocks for
introducing aromatic fluorine into structurally complex, biologically active molecules [112–114].
Jovanovic et al. (Scheme 4) [115] reported a photochemical cyclization of enallenylamides 7,
derived from trifluoromethyl-substituted cinnamic acids, to afford sterically constrained bicyclic
dihydropyridinones 8 in yields ranging from 40% to 88%. The transformation proceeds via a [2+2]
cycloaddition pathway, catalyzed by Ir(ppy)₃ (1 mol%) under blue LED irradiation in
dichloromethane at ambient temperature over 18 hours. The nitrogen substituent in the starting
enallenylamides 7 can be an alkyl group or a hydrolyzable acyl or Boc moiety, allowing for facile
deprotection and access to NH-functionalized products. This structural versatility broadens the
scope of potential biological applications for the resulting dihydropyridinones.
Scheme 4. Synthesis of trifluoromethyl-containing dihydropyridinones.
Gore and Wang (Scheme 5) [116] reported a series of intramolecular cascade reactions that enable
the synthesis of dihydroisochromenes 10 as central scaffolds within complex polycyclic
architectures. These structures feature a bridged framework comprising six-, five-, and three-
membered aliphatic rings fused to an aromatic system. The starting materials—fluorinated (E)-1-
phenyl-3-[2-((E)-styryl)phenyl]prop-2-en-1-ones 9—were subjected to visible-light irradiation (blue
LEDs) in the presence of Ir[dF(CF₃)ppy]₂(dtbbpy)PF₆ as the photocatalyst in DMSO at ambient
temperature. The reactions proceeded efficiently over 7 hours, affording the polycyclic products 10
in excellent yields ranging from 65% to 93%. Mechanistic studies suggest that the transformation
Scheme 4. Synthesis of trifluoromethyl-containing dihydropyridinones.
Scheme 5. Synthesis of fluorinated polycyclic dihydroisochromenes.
operates via an energy-transfer pathway, offering high selectivity and broad substrate tolerance.
Notably, the methodology accommodates various fluorine substitutions on the aromatic ring,
expanding its utility for the synthesis of structurally intricate, fluorinated frameworks with potential
biological relevance.
Scheme 5. Synthesis of fluorinated polycyclic dihydroisochromenes.
Zhu et al. (Scheme 6) [117] reported another example of intramolecular cascade reactions yielding
structurally intricate polycyclic frameworks. In this study, fluorinated indole derivatives 11 bearing
O-substituted oximes (as E/Z mixtures) were subjected to photochemical conditions in
dichloromethane at ambient temperature using 24 W blue LEDs in the presence of Ir(dFppy)₃ (1
mol%) as the photocatalyst. After 8 hours of irradiation, the reactions furnished indoline-fused
azetidines 12—comprising fused four-, five-, and six-membered rings—with yields ranging from
33% to 99%. This transformation proceeds via a [2+2] cycloaddition between the indole core and
the unsaturated oxime moiety. Notably, when 3-substituted analogs 13 are employed as starting
materials, the [2+2] pathway is inaccessible due to steric or electronic constraints. Nevertheless, the
reaction still undergoes an intramolecular cascade via an alternative pathway, delivering indoline-
fused piperidin-2-ones 14. These reactions were conducted under identical photochemical
conditions, yielding the corresponding bicyclic products 14 in good-to-excellent yields of 40% to
96%.
Scheme 6. Synthesis of indoline-fused azetidines and piperidinones.
Zhang et al. (Scheme 7) [118] described a photochemical strategy for the synthesis of indoline
derivatives 16 featuring fused four- and five-membered rings. The transformation proceeds via an
intramolecular [2+2] cycloaddition that simultaneously forms cyclobutene and pyrrolidine-type
motifs with virtually complete stereoselectivity. In a representative procedure, fluorine-containing
indole precursors 15 bearing an N-terminal olefinic moiety were irradiated with 30 W blue LEDs in
trifluoroethanol at –30 °C for up to 36 hours, in the presence of Ir(dFCF₃ppy)₂(dtbbpy)PF₆ (1 mol%)
Zhu et al. (Scheme 6) [117] reported an-
other example of intramolecular cascade reac-
tions yielding structurally intricate polycyclic
frameworks. In this study, fluorinated indole
derivatives 11 bearing O-substituted oximes
(as E/Z mixtures) were subjected to photo-
chemical conditions in dichloromethane at
ambient temperature using 24 W blue LEDs
in the presence of Ir(dFppy)₃ (1 mol%) as the
photocatalyst. After 8 hours of irradiation,
the reactions furnished indoline-fused azeti-
dines 12—comprising fused four-, five-, and
six-membered rings—with yields ranging from
33% to 99%. This transformation proceeds via
a [2+2] cycloaddition between the indole core
and the unsaturated oxime moiety. Notably,
when 3-substituted analogs 13 are employed as
starting materials, the [2+2] pathway is inac-
cessible due to steric or electronic constraints.
Nevertheless, the reaction still undergoes an
intramolecular cascade via an alternative path-
way, delivering indoline-fused piperidin-2-
ones 14. These reactions were conducted un-
der identical photochemical conditions, yield-
ing the corresponding bicyclic products 14 in
good-to-excellent yields of 40% to 96%.
35https://ucj.org.ua
Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
Scheme 6. Synthesis of indoline-fused azetidines and piperidinones.
operates via an energy-transfer pathway, offering high selectivity and broad substrate tolerance.
Notably, the methodology accommodates various fluorine substitutions on the aromatic ring,
expanding its utility for the synthesis of structurally intricate, fluorinated frameworks with potential
biological relevance.
Scheme 5. Synthesis of fluorinated polycyclic dihydroisochromenes.
Zhu et al. (Scheme 6) [117] reported another example of intramolecular cascade reactions yielding
structurally intricate polycyclic frameworks. In this study, fluorinated indole derivatives 11 bearing
O-substituted oximes (as E/Z mixtures) were subjected to photochemical conditions in
dichloromethane at ambient temperature using 24 W blue LEDs in the presence of Ir(dFppy)₃ (1
mol%) as the photocatalyst. After 8 hours of irradiation, the reactions furnished indoline-fused
azetidines 12—comprising fused four-, five-, and six-membered rings—with yields ranging from
33% to 99%. This transformation proceeds via a [2+2] cycloaddition between the indole core and
the unsaturated oxime moiety. Notably, when 3-substituted analogs 13 are employed as starting
materials, the [2+2] pathway is inaccessible due to steric or electronic constraints. Nevertheless, the
reaction still undergoes an intramolecular cascade via an alternative pathway, delivering indoline-
fused piperidin-2-ones 14. These reactions were conducted under identical photochemical
conditions, yielding the corresponding bicyclic products 14 in good-to-excellent yields of 40% to
96%.
Scheme 6. Synthesis of indoline-fused azetidines and piperidinones.
Zhang et al. (Scheme 7) [118] described a photochemical strategy for the synthesis of indoline
derivatives 16 featuring fused four- and five-membered rings. The transformation proceeds via an
intramolecular [2+2] cycloaddition that simultaneously forms cyclobutene and pyrrolidine-type
motifs with virtually complete stereoselectivity. In a representative procedure, fluorine-containing
indole precursors 15 bearing an N-terminal olefinic moiety were irradiated with 30 W blue LEDs in
trifluoroethanol at –30 °C for up to 36 hours, in the presence of Ir(dFCF₃ppy)₂(dtbbpy)PF₆ (1 mol%)
Zhang et al. (Scheme 7) [118] described a
photochemical strategy for the synthesis of
indoline derivatives 16 featuring fused four-
and five-membered rings. The transforma-
tion proceeds via an intramolecular [2+2]
cycloaddition that simultaneously forms cyc
lobutene and pyrrolidine-type motifs with
virtually complete stereoselectivity. In a repre
sentative procedure, fluorine-containing in-
dole precursors 15 bearing an N-terminal
olefinic moiety were irradiated with 30 W
blue LEDs in trifluoroethanol at –30 °C for
up to 36 hours, in the presence of Ir(dFCF₃p-
py)₂(dtbbpy)PF₆ (1 mol%) as the photocata-
lyst. The resulting tetracyclic products 16 were
isolated in yields ranging from 37% to 80%.
Notably, this approach exhibits excellent
functional group tolerance and is amenable
to late-stage diversification of bioactive mol-
ecules. For instance, tryptophan-based sub-
strates [R¹ = H, CH₂CH(NH₂)CO₂H] are read-
ily transformed into the corresponding poly-
cyclic targets. Given tryptophan’s central role
in peptide folding and its function as a bio
synthetic precursor to serotonin, melatonin,
and niacin (vitamin B₃), the development of
structurally complex derivatives of this essen-
tial amino acid continues to attract significant
interest in both synthetic and medicinal che
mistry [119-121].
Scheme 7. Synthesis of polycyclic indolines.
as the photocatalyst. The resulting tetracyclic products 16 were isolated in yields ranging from 37%
to 80%.
Notably, this approach exhibits excellent functional group tolerance and is amenable to late-stage
diversification of bioactive molecules. For instance, tryptophan-based substrates [R¹ = H,
CH₂CH(NH₂)CO₂H] are readily transformed into the corresponding polycyclic targets. Given
tryptophan’s central role in peptide folding and its function as a biosynthetic precursor to serotonin,
melatonin, and niacin (vitamin B₃), the development of structurally complex derivatives of this
essential amino acid continues to attract significant interest in both synthetic and medicinal
chemistry [119-121].
Scheme 7. Synthesis of polycyclic indolines.
Zhu et al. (Scheme 8) [122] reported a visible-light-induced intramolecular dearomatization of
indole derivatives via a [2+2] cycloaddition, proceeding through an energy-transfer mechanism.
This transformation enables direct access to highly strained, cyclobutane-fused angular tetracyclic
spiroindolines18—architectures typically inaccessible under thermal conditions. The products 18
were obtained in high yields (up to 99%) with excellent diastereoselectivity (>20:1 dr) under mild
reaction conditions. In a typical procedure, fluorinated indole substrates 17 were irradiated with 24
W blue LEDs in a CDM/acetonitrile mixture at ambient temperature for 48 hours, using
Ir(dFCF₃ppy)₂(dtbbpy)PF₆ (4 mol%) as the photocatalyst. The method demonstrated broad
functional group tolerance and was amenable to late-stage diversification of complex molecular
targets. Fluorination was achieved through trifluoroacetic acid (TFA) protection of the indole
nitrogen and aromatic substitution adjacent to the nitrogen, establishing a dual fluorinated motif
conducive to biological relevance and synthetic versatility.
Scheme 8. Synthesis of polycyclic spiroindolines.
Guo et al. (Scheme 9) [123] reported an efficient photocatalytic strategy for the synthesis of
isoquinolinone derivatives 20 via intramolecular carboamination of alkynes. Utilizing readily
available propargyl alcohol derivatives 19, this method demonstrates broad functional group
tolerance and accommodates both terminal and alkyl-substituted alkynes. The reactions were
performed in DMSO at 50 °C under irradiation with an 18 W compact fluorescent lamp (CFL) for
36 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
Zhu et al. (Scheme 8) [122] reported a visi-
ble-light-induced intramolecular dearomatiza-
tion of indole derivatives via a [2+2] cycload-
dition, proceeding through an energy-transfer
mechanism. This transformation enables direct
access to highly strained, cyclobutane-fused
angular tetracyclic spiroindolines18—archi-
tectures typically inaccessible under thermal
conditions. The products 18 were obtained in
high yields (up to 99%) with excellent diaste-
reoselectivity (>20:1 dr) under mild reaction
conditions. In a typical procedure, fluorinated
indole substrates 17 were irradiated with 24 W
blue LEDs in a CDM/acetonitrile mixture
at ambient temperature for 48 hours, using
Ir(dFCF₃ppy)₂(dtbbpy)PF₆ (4 mol%) as the
photocatalyst. The method demonstrated
broad functional group tolerance and was
amenable to late-stage diversification of com-
plex molecular targets. Fluorination was
achieved through trifluoroacetic acid (TFA)
protection of the indole nitrogen and aromat-
ic substitution adjacent to the nitrogen, estab-
lishing a dual fluorinated motif conducive to
biological relevance and synthetic versatility.
Scheme 8. Synthesis of polycyclic spiroindolines.
as the photocatalyst. The resulting tetracyclic products 16 were isolated in yields ranging from 37%
to 80%.
Notably, this approach exhibits excellent functional group tolerance and is amenable to late-stage
diversification of bioactive molecules. For instance, tryptophan-based substrates [R¹ = H,
CH₂CH(NH₂)CO₂H] are readily transformed into the corresponding polycyclic targets. Given
tryptophan’s central role in peptide folding and its function as a biosynthetic precursor to serotonin,
melatonin, and niacin (vitamin B₃), the development of structurally complex derivatives of this
essential amino acid continues to attract significant interest in both synthetic and medicinal
chemistry [119-121].
Scheme 7. Synthesis of polycyclic indolines.
Zhu et al. (Scheme 8) [122] reported a visible-light-induced intramolecular dearomatization of
indole derivatives via a [2+2] cycloaddition, proceeding through an energy-transfer mechanism.
This transformation enables direct access to highly strained, cyclobutane-fused angular tetracyclic
spiroindolines18—architectures typically inaccessible under thermal conditions. The products 18
were obtained in high yields (up to 99%) with excellent diastereoselectivity (>20:1 dr) under mild
reaction conditions. In a typical procedure, fluorinated indole substrates 17 were irradiated with 24
W blue LEDs in a CDM/acetonitrile mixture at ambient temperature for 48 hours, using
Ir(dFCF₃ppy)₂(dtbbpy)PF₆ (4 mol%) as the photocatalyst. The method demonstrated broad
functional group tolerance and was amenable to late-stage diversification of complex molecular
targets. Fluorination was achieved through trifluoroacetic acid (TFA) protection of the indole
nitrogen and aromatic substitution adjacent to the nitrogen, establishing a dual fluorinated motif
conducive to biological relevance and synthetic versatility.
Scheme 8. Synthesis of polycyclic spiroindolines.
Guo et al. (Scheme 9) [123] reported an efficient photocatalytic strategy for the synthesis of
isoquinolinone derivatives 20 via intramolecular carboamination of alkynes. Utilizing readily
available propargyl alcohol derivatives 19, this method demonstrates broad functional group
tolerance and accommodates both terminal and alkyl-substituted alkynes. The reactions were
performed in DMSO at 50 °C under irradiation with an 18 W compact fluorescent lamp (CFL) for
Guo et al. (Scheme 9) [123] reported an effi-
cient photocatalytic strategy for the synthesis of
isoquinolinone derivatives 20 via intramolecu-
lar carboamination of alkynes. Utilizing readily
available propargyl alcohol derivatives 19, this
method demonstrates broad functional group
tolerance and accommodates both terminal
and alkyl-substituted alkynes. The reactions
were performed in DMSO at 50 °C under irra-
diation with an 18 W compact fluorescent lamp
(CFL) for 12 hours, employing fac-Ir(ppy)₃
(2 mol%) as the photocatalyst. The target poly-
cyclic isoquinolinones 20 were obtained in
yields ranging from 26% to 86%. Importantly,
the protocol is operationally simple and readily
scalable to gram quantities. Structural diversi-
fication was achieved by incorporating either
fluorine atoms or trifluoromethyl groups on
the aromatic ring of the starting materials 19,
enabling the synthesis of fluorinated oxazoli
dinone-fused isoquinolinones 20. In addition
to their biological potential, enantiomerically
pure oxazolidinone derivatives serve as power-
ful stereocontrolling auxiliaries in asymmetric
synthesis [124–126].
Ritu et al. (Scheme 10) [127] developed an
efficient iridium–nickel dual photocatalytic
protocol for the dehydrogenation of aliphatic
N-heterocyclic compounds 21 into their cor-
responding aromatic analogs 22. This accep-
torless, redox-neutral transformation proceeds
under mild conditions—at room temperature
in ethyl acetate, under a nitrogen atmosphere—
irradiated by 5 W 450 nm blue LEDs. Remark-
37https://ucj.org.ua
Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
ably, the system employs only 0.004 mmol of
Ir(dFCF₃ppy)₂(dtbbpy)PF₆ and 0.02 mmol of
NiBr₂(dtbbpy), achieving aromatic products
22 in yields ranging from 30% to 92%, with no
evidence of overoxidation. The methodology is
compatible with commercially available fluo
rinated N-heterocyclic alkanes and accommo-
dates various functional groups. Importantly,
this transformation enables direct access to
fluorinated aromatic compounds of high syn-
thetic and commercial relevance.
Scheme 9. Preparation of oxazolidinone-fused isoquinolinones.
Scheme 10. Photocatalytic dehydrogenation of aliphatic heterocycles.
12 hours, employing fac-Ir(ppy)₃ (2 mol%) as the photocatalyst. The target polycyclic
isoquinolinones 20 were obtained in yields ranging from 26% to 86%. Importantly, the protocol is
operationally simple and readily scalable to gram quantities. Structural diversification was achieved
by incorporating either fluorine atoms or trifluoromethyl groups on the aromatic ring of the starting
materials 19, enabling the synthesis of fluorinated oxazolidinone-fused isoquinolinones 20. In
addition to their biological potential, enantiomerically pure oxazolidinone derivatives serve as
powerful stereocontrolling auxiliaries in asymmetric synthesis [124–126].
Scheme 9. Preparation of oxazolidinone-fused isoquinolinones.
Ritu et al. (Scheme 10) [127] developed an efficient iridium–nickel dual photocatalytic protocol for
the dehydrogenation of aliphatic N-heterocyclic compounds 21 into their corresponding aromatic
analogs 22. This acceptorless, redox-neutral transformation proceeds under mild conditions—at
room temperature in ethyl acetate, under a nitrogen atmosphere—irradiated by 5 W 450 nm blue
LEDs. Remarkably, the system employs only 0.004 mmol of Ir(dFCF₃ppy)₂(dtbbpy)PF₆ and 0.02
mmol of NiBr₂(dtbbpy), achieving aromatic products 22 in yields ranging from 30% to 92%, with
no evidence of overoxidation. The methodology is compatible with commercially available
fluorinated N-heterocyclic alkanes and accommodates various functional groups. Importantly, this
transformation enables direct access to fluorinated aromatic compounds of high synthetic and
commercial relevance.
Scheme 10. Photocatalytic dehydrogenation of aliphatic heterocycles.
Bimolecular reactions.
Peng et al. (Scheme 11) [128] described a visible-light-promoted C3–H alkylation of 2H-indazoles
23 and indoles 24 using sulfoxonium ylides 25. This protocol leverages readily available reagents
and accommodates a broad scope of substrates, including structurally diverse 2H-indazoles, indoles,
and sulfoxonium ylides, to afford alkylated products 26 and 27 under mild and operationally simple
conditions. Reactions were carried out in a 1,2-dichloroethane (DCE)/acetonitrile mixture at 40 °C
under an argon atmosphere, irradiated by blue LEDs (5 W) for 12 hours in the presence of fac-
Ir(ppy)₃ (5 mol%) as the photocatalyst. The desired alkylation products 26 and 27 were obtained in
isolated yields ranging from 38% to 90%. Fluorinated derivatives were synthesized via
trifluoromethyl substitution on the six-membered aromatic rings of the corresponding indazoles and
indoles, enabling structural diversification and enhancing the synthetic value of this transformation.
12 hours, employing fac-Ir(ppy)₃ (2 mol%) as the photocatalyst. The target polycyclic
isoquinolinones 20 were obtained in yields ranging from 26% to 86%. Importantly, the protocol is
operationally simple and readily scalable to gram quantities. Structural diversification was achieved
by incorporating either fluorine atoms or trifluoromethyl groups on the aromatic ring of the starting
materials 19, enabling the synthesis of fluorinated oxazolidinone-fused isoquinolinones 20. In
addition to their biological potential, enantiomerically pure oxazolidinone derivatives serve as
powerful stereocontrolling auxiliaries in asymmetric synthesis [124–126].
Scheme 9. Preparation of oxazolidinone-fused isoquinolinones.
Ritu et al. (Scheme 10) [127] developed an efficient iridium–nickel dual photocatalytic protocol for
the dehydrogenation of aliphatic N-heterocyclic compounds 21 into their corresponding aromatic
analogs 22. This acceptorless, redox-neutral transformation proceeds under mild conditions—at
room temperature in ethyl acetate, under a nitrogen atmosphere—irradiated by 5 W 450 nm blue
LEDs. Remarkably, the system employs only 0.004 mmol of Ir(dFCF₃ppy)₂(dtbbpy)PF₆ and 0.02
mmol of NiBr₂(dtbbpy), achieving aromatic products 22 in yields ranging from 30% to 92%, with
no evidence of overoxidation. The methodology is compatible with commercially available
fluorinated N-heterocyclic alkanes and accommodates various functional groups. Importantly, this
transformation enables direct access to fluorinated aromatic compounds of high synthetic and
commercial relevance.
Scheme 10. Photocatalytic dehydrogenation of aliphatic heterocycles.
Bimolecular reactions.
Peng et al. (Scheme 11) [128] described a visible-light-promoted C3–H alkylation of 2H-indazoles
23 and indoles 24 using sulfoxonium ylides 25. This protocol leverages readily available reagents
and accommodates a broad scope of substrates, including structurally diverse 2H-indazoles, indoles,
and sulfoxonium ylides, to afford alkylated products 26 and 27 under mild and operationally simple
conditions. Reactions were carried out in a 1,2-dichloroethane (DCE)/acetonitrile mixture at 40 °C
under an argon atmosphere, irradiated by blue LEDs (5 W) for 12 hours in the presence of fac-
Ir(ppy)₃ (5 mol%) as the photocatalyst. The desired alkylation products 26 and 27 were obtained in
isolated yields ranging from 38% to 90%. Fluorinated derivatives were synthesized via
trifluoromethyl substitution on the six-membered aromatic rings of the corresponding indazoles and
indoles, enabling structural diversification and enhancing the synthetic value of this transformation.
Bimolecular reactions.
Peng et al. (Scheme 11) [128] described a
visible-light-promoted C3–H alkylation of
2H-indazoles 23 and indoles 24 using sulfoxo-
nium ylides 25. This protocol leverages readily
available reagents and accommodates a broad
scope of substrates, including structurally di-
verse 2H-indazoles, indoles, and sulfoxonium
ylides, to afford alkylated products 26 and 27
under mild and operationally simple condi-
tions. Reactions were carried out in a 1,2-di-
chloroethane (DCE)/acetonitrile mixture at
40 °C under an argon atmosphere, irradiated
by blue LEDs (5 W) for 12 hours in the pre
sence of fac-Ir(ppy)₃ (5 mol%) as the photoca
talyst. The desired alkylation products 26 and
27 were obtained in isolated yields ranging
from 38% to 90%. Fluorinated derivatives were
synthesized via trifluoromethyl substitution
on the six-membered aromatic rings of the
corresponding indazoles and indoles, enabling
structural diversification and enhancing the
synthetic value of this transformation.
Ma et al. (Scheme 12) [129] developed an ef-
ficient visible-light-induced radical cascade tri-
fluoromethylation/cyclization protocol for sub-
strates 28 bearing –N=C and N-terminal alkene
motifs. Using CF₃Br as the trifluoromethylating
agent, this transformation enabled the synthe-
sis of trifluoromethyl-containing polycyclic
38 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
quinazolinones, benzimidazoles, and indoles
29 under mild conditions. The reactions were
conducted in N-methyl-2-pyrrolidone (NMP)
at 40 °C under an argon atmosphere, irradiat-
ed with 5 W blue LEDs in the presence of LiCl
(1 equiv.) and fac-Ir(ppy)₃ (5 mol%) as the
photocatalyst. The polycyclic aza-heterocycles
29 were isolated in generally good yields—up
to 80%—across a diverse array of substrates,
demonstrating broad functional group toler-
ance and synthetic versatility. Fluorination in
products 29 was introduced both via aliphatic
–CF₃ groups and through aromatic fluorine or
CF₃CO substituents on the aliphatic rings. The
use of CF₃Br, a non-hygroscopic, non-corro-
sive, and industrially abundant reagent [130],
further underscores the practicality and scala-
bility of this method. Notably, trifluoromethyl
ketones—present as key motifs in some prod-
ucts—are highly reactive toward nucleophilic
addition at the carbonyl center. Beyond their
biological significance, these intermediates
serve as valuable synthetic handles for down-
stream functionalization [131–133].
Scheme 11. Alkylation of indazoles and indoles with sulfoxonium ylides.
Scheme 11. Alkylation of indazoles and indoles with sulfoxonium ylides.
Ma et al. (Scheme 12) [129] developed an efficient visible-light-induced radical cascade
trifluoromethylation/cyclization protocol for substrates 28 bearing –N=C and N-terminal alkene
motifs. Using CF₃Br as the trifluoromethylating agent, this transformation enabled the synthesis of
trifluoromethyl-containing polycyclic quinazolinones, benzimidazoles, and indoles 29 under mild
conditions. The reactions were conducted in N-methyl-2-pyrrolidone (NMP) at 40 °C under an
argon atmosphere, irradiated with 5 W blue LEDs in the presence of LiCl (1 equiv.) and fac-Ir(ppy)₃
(5 mol%) as the photocatalyst. The polycyclic aza-heterocycles 29 were isolated in generally good
yields—up to 80%—across a diverse array of substrates, demonstrating broad functional group
tolerance and synthetic versatility. Fluorination in products 29 was introduced both via aliphatic –
CF₃ groups and through aromatic fluorine or CF₃CO substituents on the aliphatic rings. The use of
CF₃Br, a non-hygroscopic, non-corrosive, and industrially abundant reagent [130], further
underscores the practicality and scalability of this method. Notably, trifluoromethyl ketones—
present as key motifs in some products—are highly reactive toward nucleophilic addition at the
carbonyl center. Beyond their biological significance, these intermediates serve as valuable
synthetic handles for downstream functionalization [131–133].
Scheme 12. Synthesis of trifluoromethyl-containing polycyclic quinazolinones, benzimidazoles, and
indoles.
Shi et al. (Scheme 13) [134] developed a visible-light-induced deaminative [3+2] annulation
strategy between N-aminopyridinium salts 30 and alkenes 31, enabling the synthesis of
functionalized γ-lactams 32 under mild conditions. The transformation proceeds with excellent
diastereoselectivity and displays broad functional group tolerance. Reactions were performed in a
DMSO/acetonitrile mixture under an inert nitrogen atmosphere, irradiated by 15 W blue LEDs for
12 hours, in the presence of Na₂HPO₄ (2 equiv.) and fac-Ir(ppy)₃ (2 mol%) as the photocatalyst. The
γ-lactam products 32 were isolated in 40% to 75% yields, demonstrating efficient annulation across
Scheme 11. Alkylation of indazoles and indoles with sulfoxonium ylides.
Ma et al. (Scheme 12) [129] developed an efficient visible-light-induced radical cascade
trifluoromethylation/cyclization protocol for substrates 28 bearing –N=C and N-terminal alkene
motifs. Using CF₃Br as the trifluoromethylating agent, this transformation enabled the synthesis of
trifluoromethyl-containing polycyclic quinazolinones, benzimidazoles, and indoles 29 under mild
conditions. The reactions were conducted in N-methyl-2-pyrrolidone (NMP) at 40 °C under an
argon atmosphere, irradiated with 5 W blue LEDs in the presence of LiCl (1 equiv.) and fac-Ir(ppy)₃
(5 mol%) as the photocatalyst. The polycyclic aza-heterocycles 29 were isolated in generally good
yields—up to 80%—across a diverse array of substrates, demonstrating broad functional group
tolerance and synthetic versatility. Fluorination in products 29 was introduced both via aliphatic –
CF₃ groups and through aromatic fluorine or CF₃CO substituents on the aliphatic rings. The use of
CF₃Br, a non-hygroscopic, non-corrosive, and industrially abundant reagent [130], further
underscores the practicality and scalability of this method. Notably, trifluoromethyl ketones—
present as key motifs in some products—are highly reactive toward nucleophilic addition at the
carbonyl center. Beyond their biological significance, these intermediates serve as valuable
synthetic handles for downstream functionalization [131–133].
Scheme 12. Synthesis of trifluoromethyl-containing polycyclic quinazolinones, benzimidazoles, and
indoles.
Shi et al. (Scheme 13) [134] developed a visible-light-induced deaminative [3+2] annulation
strategy between N-aminopyridinium salts 30 and alkenes 31, enabling the synthesis of
functionalized γ-lactams 32 under mild conditions. The transformation proceeds with excellent
diastereoselectivity and displays broad functional group tolerance. Reactions were performed in a
DMSO/acetonitrile mixture under an inert nitrogen atmosphere, irradiated by 15 W blue LEDs for
12 hours, in the presence of Na₂HPO₄ (2 equiv.) and fac-Ir(ppy)₃ (2 mol%) as the photocatalyst. The
γ-lactam products 32 were isolated in 40% to 75% yields, demonstrating efficient annulation across
Scheme 12. Synthesis of trifluoromethyl-containing polycyclic quinazolinones,
benzimidazoles, and indoles.
Shi et al. (Scheme 13) [134] developed a
visible-light-induced deaminative [3+2] an-
nulation strategy between N-aminopyridini-
um salts 30 and alkenes 31, enabling the syn-
thesis of functionalized γ-lactams 32 under
mild conditions. The transformation proceeds
with excellent diastereoselectivity and dis-
plays broad functional group tolerance. Reac-
tions were performed in a DMSO/acetonitrile
mixture under an inert nitrogen atmosphere,
39https://ucj.org.ua
Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
irradiated by 15 W blue LEDs for 12 hours,
in the presence of Na₂HPO₄ (2 equiv.) and
fac-Ir(ppy)₃ (2 mol%) as the photocatalyst. The
γ-lactam products 32 were isolated in 40% to
75% yields, demonstrating efficient annulation
across various substrate combinations. Fluori-
nation was incorporated via either monofluo
rinated or trifluoromethyl-substituted motifs
on both precursors 30, 31, affording densely
fluorinated products 32. This dual representa-
tion of fluorine—both aliphatic and aroma
tic—enhances molecular complexity and con-
tributes to the pharmacophoric potential of
the resulting scaffolds. Formally, compounds
32 can be viewed as derivatives of tailor-made
[135] γ-amino acids, underscoring the syn-
thetic and biological relevance of fluorinated
amino acid-inspired frameworks in the design
of bioactive molecules [136, 137].
Scheme 13. Synthesis of fluorinated functionalized γ -lactams.
various substrate combinations. Fluorination was incorporated via either monofluorinated or
trifluoromethyl-substituted motifs on both precursors 30, 31, affording densely fluorinated products
32. This dual representation of fluorine—both aliphatic and aromatic—enhances molecular
complexity and contributes to the pharmacophoric potential of the resulting scaffolds. Formally,
compounds 32 can be viewed as derivatives of tailor-made [135] γ-amino acids, underscoring the
synthetic and biological relevance of fluorinated amino acid-inspired frameworks in the design of
bioactive molecules [136, 137].
Scheme 13.
Synthesis of fluorinated functionalized γ -lactams.
Liu and Patureau (Scheme 14) [138] reported a visible-light-induced photocatalytic protocol for the
functionalization of quinoxalin-2(1H)-ones 33, providing a mild, practical route to 3-substituted
quinoxalin-2(1H)-ones 35 using ubiquitous and chemically benign precursors 33 and 34. The
method showcases broad substrate scope and good functional group tolerance, furnishing a wide
array of functionalized heterocycles with strong potential in medicinal chemistry. The
transformation was performed in acetonitrile under a nitrogen atmosphere at ambient temperature,
irradiated by 40 W blue LEDs for 12 hours. The reaction employed Ir[dF(CF₃)ppy]₂(dtbpy)]PF₆ (2
mol%) as the photocatalyst, with triphenylphosphine and 1,4-diazabicyclo[2.2.2]octane (DABCO)
as additives to facilitate reactivity. Target products 35 were isolated in yields of up to 88%,
demonstrating operational simplicity and synthetic efficiency. Fluorination in the final compounds
35 arises from either aromatic fluorine or trifluoromethyl substitution, introduced through the
quinoxalinone core 33 or the anhydride 34. Notably, when R² = CF₃, the resulting product 35
structurally aligns with 2-amino-4,4,4-trifluorobutanoic acid—a privileged motif in drug design
owing to its enhanced metabolic stability and bioactivity [139–141].
Scheme 14. Functionalization of fluorinated quinoxalin-2-(1H)-ones.
Samanta et al. (Scheme 15) [142] reported a photoredox-catalyzed direct arylation of
quinoxalin-2(1H)-ones 36 using diaryliodonium triflates 37 as a convenient, stable, and cost-
effective source of aryl groups. A diverse range of quinoxalin-2(1H)-ones was successfully coupled
Liu and Patureau (Scheme 14) [138] re-
ported a visible-light-induced photocatalytic
protocol for the functionalization of quinoxa-
lin-2(1H)-ones 33, providing a mild, practical
route to 3-substituted quinoxalin-2(1H)-ones
35 using ubiquitous and chemically benign
precursors 33 and 34. The method showcas-
es broad substrate scope and good function-
al group tolerance, furnishing a wide array of
functionalized heterocycles with strong po-
tential in medicinal chemistry. The transfor-
mation was performed in acetonitrile under a
nitrogen atmosphere at ambient temperature,
irradiated by 40 W blue LEDs for 12 hours. The
reaction employed Ir[dF(CF₃)ppy]₂(dtbpy)]
PF₆ (2 mol%) as the photocatalyst, with triphe-
nylphosphine and 1,4-diazabicyclo[2.2.2]oc-
tane (DABCO) as additives to facilitate reacti
vity. Target products 35 were isolated in yields
of up to 88%, demonstrating operational sim-
plicity and synthetic efficiency. Fluorination in
the final compounds 35 arises from either aro-
matic fluorine or trifluoromethyl substitution,
introduced through the quinoxalinone core 33
or the anhydride 34. Notably, when R² = CF₃,
the resulting product 35 structurally aligns
with 2-amino-4,4,4-trifluorobutanoic acid—a
privileged motif in drug design owing to its
enhanced metabolic stability and bioactivity
[139–141].
Samanta et al. (Scheme 15) [142] reported
a photoredox-catalyzed direct arylation of qui-
noxalin-2(1H)-ones 36 using diaryliodonium
triflates 37 as a convenient, stable, and cost-ef-
fective source of aryl groups. A diverse range of
quinoxalin-2(1H)-ones was successfully cou-
pled with structurally and electronically varied
diaryliodonium salts, enabling efficient syn-
thesis of pharmaceutically valuable 3-arylqui-
noxalin-2(1H)-ones 38. The protocol is notable
for its operational simplicity, ambient reaction
conditions, broad substrate scope, excellent
40 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
functional group tolerance, and scalability. Re-
actions were conducted in acetonitrile at room
temperature under blue LED irradiation for 24
hours, employing Ru(bpy)3Cl2·6H2O (5 mol%)
as the photocatalyst. Target arylated products
38 were obtained in yields ranging from 24%
to 90%. Fluorination in products 38 is intro-
duced via the aryl moiety of diaryliodonium
triflates 37, incorporating either a single flu-
orine atom, a trifluoromethyl group, or a tri-
fluoromethoxy substituent. Notably, the aro-
matic trifluoromethoxy group has garnered
increasing attention due to its prevalence in a
growing number of successful pharmaceuticals
and agrochemicals [143, 144], attributed to its
unique electronic properties and favorable li-
pophilicity.
various substrate combinations. Fluorination was incorporated via either monofluorinated or
trifluoromethyl-substituted motifs on both precursors 30, 31, affording densely fluorinated products
32. This dual representation of fluorine—both aliphatic and aromatic—enhances molecular
complexity and contributes to the pharmacophoric potential of the resulting scaffolds. Formally,
compounds 32 can be viewed as derivatives of tailor-made [135] γ-amino acids, underscoring the
synthetic and biological relevance of fluorinated amino acid-inspired frameworks in the design of
bioactive molecules [136, 137].
Scheme 13.
Synthesis of fluorinated functionalized γ -lactams.
Liu and Patureau (Scheme 14) [138] reported a visible-light-induced photocatalytic protocol for the
functionalization of quinoxalin-2(1H)-ones 33, providing a mild, practical route to 3-substituted
quinoxalin-2(1H)-ones 35 using ubiquitous and chemically benign precursors 33 and 34. The
method showcases broad substrate scope and good functional group tolerance, furnishing a wide
array of functionalized heterocycles with strong potential in medicinal chemistry. The
transformation was performed in acetonitrile under a nitrogen atmosphere at ambient temperature,
irradiated by 40 W blue LEDs for 12 hours. The reaction employed Ir[dF(CF₃)ppy]₂(dtbpy)]PF₆ (2
mol%) as the photocatalyst, with triphenylphosphine and 1,4-diazabicyclo[2.2.2]octane (DABCO)
as additives to facilitate reactivity. Target products 35 were isolated in yields of up to 88%,
demonstrating operational simplicity and synthetic efficiency. Fluorination in the final compounds
35 arises from either aromatic fluorine or trifluoromethyl substitution, introduced through the
quinoxalinone core 33 or the anhydride 34. Notably, when R² = CF₃, the resulting product 35
structurally aligns with 2-amino-4,4,4-trifluorobutanoic acid—a privileged motif in drug design
owing to its enhanced metabolic stability and bioactivity [139–141].
Scheme 14. Functionalization of fluorinated quinoxalin-2-(1H)-ones.
Samanta et al. (Scheme 15) [142] reported a photoredox-catalyzed direct arylation of
quinoxalin-2(1H)-ones 36 using diaryliodonium triflates 37 as a convenient, stable, and cost-
effective source of aryl groups. A diverse range of quinoxalin-2(1H)-ones was successfully coupled
Scheme 14. Functionalization of fluorinated quinoxalin-2-(1H)-ones.
Scheme 15. Synthesis of fluorinated 3-arylquinoxalin-2-(1H)-ones.
with structurally and electronically varied diaryliodonium salts, enabling efficient synthesis of
pharmaceutically valuable 3-arylquinoxalin-2(1H)-ones 38. The protocol is notable for its
operational simplicity, ambient reaction conditions, broad substrate scope, excellent functional
group tolerance, and scalability. Reactions were conducted in acetonitrile at room temperature under
blue LED irradiation for 24 hours, employing Ru(bpy)3Cl2·6H2O (5 mol%) as the photocatalyst.
Target arylated products 38 were obtained in yields ranging from 24% to 90%. Fluorination in
products 38 is introduced via the aryl moiety of diaryliodonium triflates 37, incorporating either a
single fluorine atom, a trifluoromethyl group, or a trifluoromethoxy substituent. Notably, the
aromatic trifluoromethoxy group has garnered increasing attention due to its prevalence in a
growing number of successful pharmaceuticals and agrochemicals [143, 144], attributed to its
unique electronic properties and favorable lipophilicity.
Scheme 15. Synthesis of fluorinated 3-arylquinoxalin-2-(1H)-ones.
Xie et al. (Scheme 16) [145] developed an efficient and sustainable strategy for the synthesis of 3-
alkyl(aryl)quinoxalin-2(1H)-ones 41 via visible-light-induced decarboxylative alkylation/arylation
of quinoxalin-2(1H)-ones 39 using phenyliodine(III) dicarboxylates 40 as alkyl/aryl sources. The
reaction proceeds under ambient conditions in eco-friendly PEG-200, highlighting its green
chemistry credentials. Employing Ru(bpy)3Cl2·6H2O (1 mol%) as the photocatalyst and irradiating
with 3 W blue LEDs, the process delivers a range of 3-substituted quinoxalin-2(1H)-ones 41 in
yields of up to 93%, with reaction times varying between 6 and 12 hours. Notably, the ruthenium(II)
catalytic system remains effective over five consecutive cycles without significant loss of activity.
Fluorinated analogs were accessed through incorporation of aryl motifs bearing either a single
fluorine atom or a trifluoromethyl group, reinforcing the method's relevance for medicinal
chemistry applications.
Scheme 16. Synthesis of 3-alkyl(aryl)quinoxalin-2(1H)-ones
Wang et al. (Scheme 17) [146] described a mild and efficient visible-light-induced atom transfer
radical addition and cyclization of benzene-tethered 1,7-enynes 42 and nitrogen-tethered 1,6-enynes
45 with perfluoroalkyl halides 43, yielding halo-perfluorinated 4-methylenequinolin-2(1H)-ones 44
and 3-methylenepyrrolidine derivatives 46, respectively. Reactions were carried out in 1,4-dioxane
Xie et al. (Scheme 16) [145] developed an
efficient and sustainable strategy for the syn-
thesis of 3-alkyl(aryl)quinoxalin-2(1H)-ones
41 via visible-light-induced decarboxylative
alkylation/arylation of quinoxalin-2(1H)-ones
39 using phenyliodine(III) dicarboxylates 40 as
alkyl/aryl sources. The reaction proceeds under
ambient conditions in eco-friendly PEG-200,
highlighting its green chemistry credentials.
Employing Ru(bpy)3Cl2·6H2O (1 mol%) as the
photocatalyst and irradiating with 3 W blue
LEDs, the process delivers a range of 3-substi-
tuted quinoxalin-2(1H)-ones 41 in yields of up
to 93%, with reaction times varying between 6
and 12 hours. Notably, the ruthenium(II) cata-
lytic system remains effective over five consec-
utive cycles without significant loss of activity.
Fluorinated analogs were accessed through in-
corporation of aryl motifs bearing either a sin-
gle fluorine atom or a trifluoromethyl group,
reinforcing the method’s relevance for medici-
nal chemistry applications.
41https://ucj.org.ua
Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
Scheme 16. Synthesis of 3-alkyl(aryl)quinoxalin-2(1H)-ones
with structurally and electronically varied diaryliodonium salts, enabling efficient synthesis of
pharmaceutically valuable 3-arylquinoxalin-2(1H)-ones 38. The protocol is notable for its
operational simplicity, ambient reaction conditions, broad substrate scope, excellent functional
group tolerance, and scalability. Reactions were conducted in acetonitrile at room temperature under
blue LED irradiation for 24 hours, employing Ru(bpy)3Cl2·6H2O (5 mol%) as the photocatalyst.
Target arylated products 38 were obtained in yields ranging from 24% to 90%. Fluorination in
products 38 is introduced via the aryl moiety of diaryliodonium triflates 37, incorporating either a
single fluorine atom, a trifluoromethyl group, or a trifluoromethoxy substituent. Notably, the
aromatic trifluoromethoxy group has garnered increasing attention due to its prevalence in a
growing number of successful pharmaceuticals and agrochemicals [143, 144], attributed to its
unique electronic properties and favorable lipophilicity.
Scheme 15. Synthesis of fluorinated 3-arylquinoxalin-2-(1H)-ones.
Xie et al. (Scheme 16) [145] developed an efficient and sustainable strategy for the synthesis of 3-
alkyl(aryl)quinoxalin-2(1H)-ones 41 via visible-light-induced decarboxylative alkylation/arylation
of quinoxalin-2(1H)-ones 39 using phenyliodine(III) dicarboxylates 40 as alkyl/aryl sources. The
reaction proceeds under ambient conditions in eco-friendly PEG-200, highlighting its green
chemistry credentials. Employing Ru(bpy)3Cl2·6H2O (1 mol%) as the photocatalyst and irradiating
with 3 W blue LEDs, the process delivers a range of 3-substituted quinoxalin-2(1H)-ones 41 in
yields of up to 93%, with reaction times varying between 6 and 12 hours. Notably, the ruthenium(II)
catalytic system remains effective over five consecutive cycles without significant loss of activity.
Fluorinated analogs were accessed through incorporation of aryl motifs bearing either a single
fluorine atom or a trifluoromethyl group, reinforcing the method's relevance for medicinal
chemistry applications.
Scheme 16. Synthesis of 3-alkyl(aryl)quinoxalin-2(1H)-ones
Wang et al. (Scheme 17) [146] described a mild and efficient visible-light-induced atom transfer
radical addition and cyclization of benzene-tethered 1,7-enynes 42 and nitrogen-tethered 1,6-enynes
45 with perfluoroalkyl halides 43, yielding halo-perfluorinated 4-methylenequinolin-2(1H)-ones 44
and 3-methylenepyrrolidine derivatives 46, respectively. Reactions were carried out in 1,4-dioxane
Wang et al. (Scheme 17) [146] described a
mild and efficient visible-light-induced atom
transfer radical addition and cyclization of
benzene-tethered 1,7-enynes 42 and nitro-
gen-tethered 1,6-enynes 45 with perfluoro-
alkyl halides 43, yielding halo-perfluorinat-
ed 4-methylenequinolin-2(1H)-ones 44 and
3-methylenepyrrolidine derivatives 46, respec-
tively. Reactions were carried out in 1,4-diox-
ane at ambient temperature for 24 hours, uti-
lizing K₃PO₄ (2 equiv.) as an additive, fac-Ir(p-
py)₃ as the photocatalyst, and irradiation from
5 W blue LEDs. Products 44 and 46 were ob-
tained in isolated yields ranging from 10% to
86% and 53% to 89%, respectively. This meth-
odology enables the efficient incorporation of a
broad spectrum of perfluoroalkyl groups—in-
cluding n-C₃F₇, n-C₄F₉, n-C₆F₁₃, n-C₈F₁₇, and
n-C₁₀F₂₁—into heterocyclic frameworks of
pharmacological relevance. However, it is im-
portant to note that while some perfluorinat-
ed compounds find utility in life sciences and
materials chemistry, many members of this
class—commonly referred to as per- and poly-
fluoroalkyl substances (PFAS)—pose serious
environmental hazards due to their persistence
and bioaccumulative potential [147–149]. Ac-
cordingly, the synthesis and application of such
substances should be approached with strict
regulatory oversight and pursued only when
no viable alternatives exist.
Scheme 17. Preparation of halo-perfluorinated 4-methylenequinolin-2(1H)-one
and 3-methylenepyrrolidine derivatives.
at ambient temperature for 24 hours, utilizing K₃PO₄ (2 equiv.) as an additive, fac-Ir(ppy)₃ as the
photocatalyst, and irradiation from 5 W blue LEDs. Products 44 and 46 were obtained in isolated
yields ranging from 10% to 86% and 53% to 89%, respectively. This methodology enables the
efficient incorporation of a broad spectrum of perfluoroalkyl groups—including n-C₃F₇, n-C₄F₉, n-
C₆F₁₃, n-C₈F₁₇, and n-C₁₀F₂₁—into heterocyclic frameworks of pharmacological relevance.
However, it is important to note that while some perfluorinated compounds find utility in life
sciences and materials chemistry, many members of this class—commonly referred to as per- and
polyfluoroalkyl substances (PFAS)—pose serious environmental hazards due to their persistence
and bioaccumulative potential [147–149]. Accordingly, the synthesis and application of such
substances should be approached with strict regulatory oversight and pursued only when no viable
alternatives exist.
Scheme 17. Preparation of halo-perfluorinated 4-methylenequinolin-2(1H)-one and 3-
methylenepyrrolidine derivatives.
Liu et al. (Scheme 18) [150] reported a practical visible-light-catalyzed tandem radical cyclization
of N-propargylindoles 47 with acyl chlorides 48 to access 2-acyl-9H-pyrrolo[1,2-a]indoles 49. The
transformation involves a sequential mechanism: addition of the acyl radical to the carbon–carbon
triple bond, intramolecular cyclization at the C2-position of the indole ring, followed by
isomerization of the resulting carbon–carbon double bond. Reactions were performed in acetonitrile
under an argon atmosphere at 100 °C for 20 hours, using triethylamine to neutralize the released
HCl. Photocatalysis was enabled by Ir(ppy)₃ (1 mol%) under irradiation from 5 W blue LEDs.
Target compounds 49 were obtained in yields of up to 86%. Fluorinated analogs were represented
by the presence of aromatic fluorine substituents on the benzene ring in both the starting indoles 47
and the resulting products 49, contributing to potential structural diversification relevant to
medicinal chemistry.
Scheme 18. Preparation of 2-acyl-9H-pyrrolo[1,2-a]indoles.
42 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
Liu et al. (Scheme 18) [150] reported a prac-
tical visible-light-catalyzed tandem radical cyc
lization of N-propargylindoles 47 with acyl
chlorides 48 to access 2-acyl-9H-pyrrolo[1,2-a]
indoles 49. The transformation involves a se-
quential mechanism: addition of the acyl rad-
ical to the carbon–carbon triple bond, intra-
molecular cyclization at the C2-position of the
indole ring, followed by isomerization of the re-
sulting carbon–carbon double bond. Reactions
were performed in acetonitrile under an argon
atmosphere at 100 °C for 20 hours, using tri-
ethylamine to neutralize the released HCl. Pho-
tocatalysis was enabled by Ir(ppy)₃ (1 mol%)
under irradiation from 5 W blue LEDs. Target
compounds 49 were obtained in yields of up to
86%. Fluorinated analogs were represented by
the presence of aromatic fluorine substituents
on the benzene ring in both the starting indoles
47 and the resulting products 49, contributing
to potential structural diversification relevant
to medicinal chemistry.
at ambient temperature for 24 hours, utilizing K₃PO₄ (2 equiv.) as an additive, fac-Ir(ppy)₃ as the
photocatalyst, and irradiation from 5 W blue LEDs. Products 44 and 46 were obtained in isolated
yields ranging from 10% to 86% and 53% to 89%, respectively. This methodology enables the
efficient incorporation of a broad spectrum of perfluoroalkyl groups—including n-C₃F₇, n-C₄F₉, n-
C₆F₁₃, n-C₈F₁₇, and n-C₁₀F₂₁—into heterocyclic frameworks of pharmacological relevance.
However, it is important to note that while some perfluorinated compounds find utility in life
sciences and materials chemistry, many members of this class—commonly referred to as per- and
polyfluoroalkyl substances (PFAS)—pose serious environmental hazards due to their persistence
and bioaccumulative potential [147–149]. Accordingly, the synthesis and application of such
substances should be approached with strict regulatory oversight and pursued only when no viable
alternatives exist.
Scheme 17. Preparation of halo-perfluorinated 4-methylenequinolin-2(1H)-one and 3-
methylenepyrrolidine derivatives.
Liu et al. (Scheme 18) [150] reported a practical visible-light-catalyzed tandem radical cyclization
of N-propargylindoles 47 with acyl chlorides 48 to access 2-acyl-9H-pyrrolo[1,2-a]indoles 49. The
transformation involves a sequential mechanism: addition of the acyl radical to the carbon–carbon
triple bond, intramolecular cyclization at the C2-position of the indole ring, followed by
isomerization of the resulting carbon–carbon double bond. Reactions were performed in acetonitrile
under an argon atmosphere at 100 °C for 20 hours, using triethylamine to neutralize the released
HCl. Photocatalysis was enabled by Ir(ppy)₃ (1 mol%) under irradiation from 5 W blue LEDs.
Target compounds 49 were obtained in yields of up to 86%. Fluorinated analogs were represented
by the presence of aromatic fluorine substituents on the benzene ring in both the starting indoles 47
and the resulting products 49, contributing to potential structural diversification relevant to
medicinal chemistry.
Scheme 18. Preparation of 2-acyl-9H-pyrrolo[1,2-a]indoles.Scheme 18. Preparation of 2-acyl-9H-pyrrolo[1,2-a]indoles.
Santos et al. (Scheme 19) [151] reported a
visible-light-induced radical cascade for the
synthesis of 2-sulfenylindoles 52 via thiyl radi
cal coupling with ortho-substituted arylisocy-
anides 50, followed by intramolecular cycliza-
tion and aromatization. The key thiyl radicals
are rapidly generated through a hydrogen atom
transfer (HAT) event from thiol precursor 51,
enabling a redox-neutral transformation. The
protocol exhibits broad substrate scope, excel-
lent functional group tolerance, and proceeds
under mild conditions. Notably, a continuous
flow adaptation provides efficient scalabil-
ity, with reduced residence time and process
intensification advantages. Reactions were
conducted in DMSO under an argon atmos-
phere at ambient temperature for over 3 hours
using p-toluidine (0.5 equiv.) as an additive.
[Ru(bpy)3](PF₆)2 (1 mol%) served as the pho-
tocatalyst, and irradiation was provided by 34
W blue LEDs. Desired sulfenylated products
52 were isolated in yields of up to 95%. Fluo
rinated derivatives were accessed via aryliso-
cyanide precursors bearing aromatic fluorine
substituents, which were retained in the final
products. These fluorinated motifs contribute
to structural diversification and enhance the
relevance of this method for medicinal che
mistry applications.
Zhu et al. (Scheme 20) [152] reported a re-
ductive radical relay strategy for the synthesis
of fused benzo[e]isoindole-1,3,5-triones 55 via
the visible-light-mediated reaction of α-bro-
mo ketones 53 with maleimides 54, catalyzed
by Ir(ppy)₃ under mild conditions. The trans-
formation proceeds through a mechanistically
elegant cascade involving C(sp³)–Br/C(sp²)–H
functionalization, consecutive C–C bond for-
43https://ucj.org.ua
Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
mations, and oxidative aromatization. Reac-
tions were conducted in acetonitrile at ambi-
ent temperature for 20 hours under nitrogen,
using K₂HPO₄ (1 equiv.) as an additive and
7.5 W blue LEDs as the light source. The pho-
tocatalyst Ir(ppy)₃ was employed at a loading
of 2 mol%. Target products 55 were obtained
in isolated yields ranging from 51% to 89%.
Fluorinated derivatives were accessed using
trifluoromethyl-substituted α-bromo ketones
53, resulting in final products 55 bearing ar-
omatic CF₃ groups. These fluorinated motifs
enhance molecular lipophilicity and metabol-
ic stability, underscoring the relevance of this
strategy for fluorine-rich scaffold development
in medicinal chemistry.
Scheme 19. Synthesis of 2-sulfenylindoles.
Scheme 20. Preparation of fused benzo[e]isoindole-1,3,5-triones.
Santos et al. (Scheme 19) [151] reported a visible-light-induced radical cascade for the synthesis of
2-sulfenylindoles 52 via thiyl radical coupling with ortho-substituted arylisocyanides 50, followed
by intramolecular cyclization and aromatization. The key thiyl radicals are rapidly generated
through a hydrogen atom transfer (HAT) event from thiol precursor 51, enabling a redox-neutral
transformation. The protocol exhibits broad substrate scope, excellent functional group tolerance,
and proceeds under mild conditions. Notably, a continuous flow adaptation provides efficient
scalability, with reduced residence time and process intensification advantages. Reactions were
conducted in DMSO under an argon atmosphere at ambient temperature for over 3 hours using p-
toluidine (0.5 equiv.) as an additive. [Ru(bpy)3](PF₆)2 (1 mol%) served as the photocatalyst, and
irradiation was provided by 34 W blue LEDs. Desired sulfenylated products 52 were isolated in
yields of up to 95%. Fluorinated derivatives were accessed via arylisocyanide precursors bearing
aromatic fluorine substituents, which were retained in the final products. These fluorinated motifs
contribute to structural diversification and enhance the relevance of this method for medicinal
chemistry applications.
Scheme 19. Synthesis of 2-sulfenylindoles.
Zhu et al. (Scheme 20) [152] reported a reductive radical relay strategy for the synthesis of fused
benzo[e]isoindole-1,3,5-triones 55 via the visible-light-mediated reaction of α-bromo ketones 53
with maleimides 54, catalyzed by Ir(ppy)₃ under mild conditions. The transformation proceeds
through a mechanistically elegant cascade involving C(sp³)–Br/C(sp²)–H functionalization,
consecutive C–C bond formations, and oxidative aromatization. Reactions were conducted in
acetonitrile at ambient temperature for 20 hours under nitrogen, using K₂HPO₄ (1 equiv.) as an
additive and 7.5 W blue LEDs as the light source. The photocatalyst Ir(ppy)₃ was employed at a
loading of 2 mol%. Target products 55 were obtained in isolated yields ranging from 51% to 89%.
Fluorinated derivatives were accessed using trifluoromethyl-substituted α-bromo ketones 53,
resulting in final products 55 bearing aromatic CF₃ groups. These fluorinated motifs enhance
molecular lipophilicity and metabolic stability, underscoring the relevance of this strategy for
fluorine-rich scaffold development in medicinal chemistry.
Scheme 20. Preparation of fused benzo[e]isoindole-1,3,5-triones.
Fan et al. (Scheme 21) [153] developed a visible-light-mediated approach for generating acyl
radicals from oxime ester 57 via selective C–C bond activation. Upon irradiation with blue LEDs, a
Santos et al. (Scheme 19) [151] reported a visible-light-induced radical cascade for the synthesis of
2-sulfenylindoles 52 via thiyl radical coupling with ortho-substituted arylisocyanides 50, followed
by intramolecular cyclization and aromatization. The key thiyl radicals are rapidly generated
through a hydrogen atom transfer (HAT) event from thiol precursor 51, enabling a redox-neutral
transformation. The protocol exhibits broad substrate scope, excellent functional group tolerance,
and proceeds under mild conditions. Notably, a continuous flow adaptation provides efficient
scalability, with reduced residence time and process intensification advantages. Reactions were
conducted in DMSO under an argon atmosphere at ambient temperature for over 3 hours using p-
toluidine (0.5 equiv.) as an additive. [Ru(bpy)3](PF₆)2 (1 mol%) served as the photocatalyst, and
irradiation was provided by 34 W blue LEDs. Desired sulfenylated products 52 were isolated in
yields of up to 95%. Fluorinated derivatives were accessed via arylisocyanide precursors bearing
aromatic fluorine substituents, which were retained in the final products. These fluorinated motifs
contribute to structural diversification and enhance the relevance of this method for medicinal
chemistry applications.
Scheme 19. Synthesis of 2-sulfenylindoles.
Zhu et al. (Scheme 20) [152] reported a reductive radical relay strategy for the synthesis of fused
benzo[e]isoindole-1,3,5-triones 55 via the visible-light-mediated reaction of α-bromo ketones 53
with maleimides 54, catalyzed by Ir(ppy)₃ under mild conditions. The transformation proceeds
through a mechanistically elegant cascade involving C(sp³)–Br/C(sp²)–H functionalization,
consecutive C–C bond formations, and oxidative aromatization. Reactions were conducted in
acetonitrile at ambient temperature for 20 hours under nitrogen, using K₂HPO₄ (1 equiv.) as an
additive and 7.5 W blue LEDs as the light source. The photocatalyst Ir(ppy)₃ was employed at a
loading of 2 mol%. Target products 55 were obtained in isolated yields ranging from 51% to 89%.
Fluorinated derivatives were accessed using trifluoromethyl-substituted α-bromo ketones 53,
resulting in final products 55 bearing aromatic CF₃ groups. These fluorinated motifs enhance
molecular lipophilicity and metabolic stability, underscoring the relevance of this strategy for
fluorine-rich scaffold development in medicinal chemistry.
Scheme 20. Preparation of fused benzo[e]isoindole-1,3,5-triones.
Fan et al. (Scheme 21) [153] developed a visible-light-mediated approach for generating acyl
radicals from oxime ester 57 via selective C–C bond activation. Upon irradiation with blue LEDs, a
Fan et al. (Scheme 21) [153] developed a
visible-light-mediated approach for generating
acyl radicals from oxime ester 57 via selective
C–C bond activation. Upon irradiation with
blue LEDs, a single-electron transfer (SET) oc-
curs from fac-Ir(ppy)3 (1 mol%) to oxime 57,
triggering rapid β-fragmentation to produce
aliphatic acyl radicals. These intermediates
are efficiently trapped by various Michael ac-
ceptors 56, yielding fluorinated oxindoles 58
in 34% to 94% yields. The reactions proceed
in 1,2-dichloroethane (DCE) under an argon
atmosphere over 4 hours. The presence of
fluorine on the aromatic ring in the oxindole
products underscores the value of this proto-
col for the synthesis of fluorinated oxindoles,
a scaffold of significant interest in medicinal
chemistry [154].
The aza-Paternò–Büchi reaction is a [2+2]-
cycloaddition between alkenes and imines that
affords azetidines, four-membered nitrogen-
containing heterocycles. To expand the syn-
thetic utility of this transformation, Wearing
et al. (Scheme 22) [155] demonstrated that
appropriate matching of frontier molecular
orbital energies between alkenes 59 and acyc
lic oximes 60 enables a visible-light-driven
aza-Paternò–Büchi reaction via triplet energy
transfer (EnT) catalysis. Under irradiation at
427 nm, the reaction proceeds in acetonitrile
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RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
for up to 24 hours, employing 1 mol% of Ir[d-
F(CF₃)ppy]₂(dtbpy)]PF₆ as photocatalyst. The
methodology affords azetidines 61 in yields of
up to 80%. Notably, the presence of fluorine on
the aromatic rings of both the starting alkenes
59 and the azetidine products 61 highlights
the relevance of this approach for constructing
fluorinated nitrogen heterocycles, which are
valuable in medicinal chemistry.
Scheme 21. Synthesis of fluorinated oxindoles.
Scheme 22. Synthesis of fluorinated azetidines.
single-electron transfer (SET) occurs from fac-Ir(ppy)3 (1 mol%) to oxime 57, triggering rapid β-
fragmentation to produce aliphatic acyl radicals. These intermediates are efficiently trapped by
various Michael acceptors 56, yielding fluorinated oxindoles 58 in 34% to 94% yields. The
reactions proceed in 1,2-dichloroethane (DCE) under an argon atmosphere over 4 hours. The
presence of fluorine on the aromatic ring in the oxindole products underscores the value of this
protocol for the synthesis of fluorinated oxindoles, a scaffold of significant interest in medicinal
chemistry [154].
Scheme 21. Synthesis of fluorinated oxindoles.
The aza-Paternò–Büchi reaction is a [2+2]-cycloaddition between alkenes and imines that affords
azetidines, four-membered nitrogen-containing heterocycles. To expand the synthetic utility of this
transformation, Wearing et al. (Scheme 22) [155] demonstrated that appropriate matching of
frontier molecular orbital energies between alkenes 59 and acyclic oximes 60 enables a visible-
light-driven aza-Paternò–Büchi reaction via triplet energy transfer (EnT) catalysis. Under
irradiation at 427 nm, the reaction proceeds in acetonitrile for up to 24 hours, employing 1 mol% of
Ir[dF(CF₃)ppy]₂(dtbpy)]PF₆ as photocatalyst. The methodology affords azetidines 61 in yields of up
to 80%. Notably, the presence of fluorine on the aromatic rings of both the starting alkenes 59 and
the azetidine products 61 highlights the relevance of this approach for constructing fluorinated
nitrogen heterocycles, which are valuable in medicinal chemistry.
Scheme 22. Synthesis of fluorinated azetidines.
Yu et al. (Scheme 23) [156] reported a visible-light-enabled synthesis of tricyclic
tetrahydrocarbazoles 64 via the reaction of indole-tethered alkenes 62 with arylsulfonyl chlorides 63
as sulfonyl surrogates. The transformation proceeds through a sequence involving photoreductive
activation of the sulfonyl chloride, followed by sulfonylation and intramolecular cyclization. Under
irradiation with blue LEDs for 3 hours, the reaction employs fac-Ir(ppy)3 (1 mol%) as photocatalyst,
Hünig’s base (4 equiv.) to scavenge HCl, and CH₂Cl₂ as the solvent. This mild and operationally
simple protocol delivers diverse multi-substituted tetrahydrocarbazoles 64 in yields of up to 83%,
and is amenable to gram-scale synthesis. The incorporation of fluorine substituents on the aromatic
rings of both starting materials allows for systematic modulation of fluorine patterns in the resulting
products, enabling structure–activity relationship studies relevant to medicinal chemistry.
single-electron transfer (SET) occurs from fac-Ir(ppy)3 (1 mol%) to oxime 57, triggering rapid β-
fragmentation to produce aliphatic acyl radicals. These intermediates are efficiently trapped by
various Michael acceptors 56, yielding fluorinated oxindoles 58 in 34% to 94% yields. The
reactions proceed in 1,2-dichloroethane (DCE) under an argon atmosphere over 4 hours. The
presence of fluorine on the aromatic ring in the oxindole products underscores the value of this
protocol for the synthesis of fluorinated oxindoles, a scaffold of significant interest in medicinal
chemistry [154].
Scheme 21. Synthesis of fluorinated oxindoles.
The aza-Paternò–Büchi reaction is a [2+2]-cycloaddition between alkenes and imines that affords
azetidines, four-membered nitrogen-containing heterocycles. To expand the synthetic utility of this
transformation, Wearing et al. (Scheme 22) [155] demonstrated that appropriate matching of
frontier molecular orbital energies between alkenes 59 and acyclic oximes 60 enables a visible-
light-driven aza-Paternò–Büchi reaction via triplet energy transfer (EnT) catalysis. Under
irradiation at 427 nm, the reaction proceeds in acetonitrile for up to 24 hours, employing 1 mol% of
Ir[dF(CF₃)ppy]₂(dtbpy)]PF₆ as photocatalyst. The methodology affords azetidines 61 in yields of up
to 80%. Notably, the presence of fluorine on the aromatic rings of both the starting alkenes 59 and
the azetidine products 61 highlights the relevance of this approach for constructing fluorinated
nitrogen heterocycles, which are valuable in medicinal chemistry.
Scheme 22. Synthesis of fluorinated azetidines.
Yu et al. (Scheme 23) [156] reported a visible-light-enabled synthesis of tricyclic
tetrahydrocarbazoles 64 via the reaction of indole-tethered alkenes 62 with arylsulfonyl chlorides 63
as sulfonyl surrogates. The transformation proceeds through a sequence involving photoreductive
activation of the sulfonyl chloride, followed by sulfonylation and intramolecular cyclization. Under
irradiation with blue LEDs for 3 hours, the reaction employs fac-Ir(ppy)3 (1 mol%) as photocatalyst,
Hünig’s base (4 equiv.) to scavenge HCl, and CH₂Cl₂ as the solvent. This mild and operationally
simple protocol delivers diverse multi-substituted tetrahydrocarbazoles 64 in yields of up to 83%,
and is amenable to gram-scale synthesis. The incorporation of fluorine substituents on the aromatic
rings of both starting materials allows for systematic modulation of fluorine patterns in the resulting
products, enabling structure–activity relationship studies relevant to medicinal chemistry.
Yu et al. (Scheme 23) [156] reported a vis-
ible-light-enabled synthesis of tricyclic tetra
hydrocarbazoles 64 via the reaction of in-
dole-tethered alkenes 62 with arylsulfonyl
chlorides 63 as sulfonyl surrogates. The trans-
formation proceeds through a sequence involv-
ing photoreductive activation of the sulfonyl
chloride, followed by sulfonylation and intra-
molecular cyclization. Under irradiation with
blue LEDs for 3 hours, the reaction employs
fac-Ir(ppy)3 (1 mol%) as photocatalyst, Hünig’s
base (4 equiv.) to scavenge HCl, and CH₂Cl₂ as
the solvent. This mild and operationally sim-
ple protocol delivers diverse multi-substitut-
ed tetrahydrocarbazoles 64 in yields of up to
83%, and is amenable to gram-scale synthesis.
The incorporation of fluorine substituents on
the aromatic rings of both starting materials
allows for systematic modulation of fluorine
patterns in the resulting products, enabling
structure–activity relationship studies relevant
to medicinal chemistry.
Scheme 23. Synthesis of fluorinated tetrahydrocarbazoles.
Scheme 23. Synthesis of fluorinated tetrahydrocarbazoles.
Hou et al. (Scheme 24) [157] reported a visible-light-induced chlorotrifluoromethylative cyclization
strategy for synthesizing chlorotrifluoromethylated cyclic scaffolds. The method leverages
photogenerated trifluoromethyl radicals to initiate a cascade involving radical addition, cyclization,
and subsequent chlorination. Employing terminal alkene-derived enynes 65 and
trifluoromethanesulfonyl chloride 66, this protocol delivers regio- and stereoselective access to
pyrrolidines and cyclopentanes 67 bearing trifluoromethyl group, with yields ranging from 70–75%.
Reactions are performed in 1,2-dichloromethane (DCM) under an argon atmosphere at ambient
temperature, using K₂HPO₄ (5 equiv.) as an additive and Ru(bpy)3Cl₂ (5 mol%) as photocatalyst
under 23 W fluorescent lamp irradiation. The resulting trifluoromethylated pyrrolidines are of
significant biomedical interest and can be further derivatized via the embedded vinylchloride
functionality, enabling downstream molecular elaboration.
Scheme 24. Synthesis of trifluoromethyl-containing pyrrolidine and cyclopentane.
Cardinale et al. (Scheme 25) [158] reported a photocatalytic strategy for synthesizing 1,5-diaryl
pyrazoles 70 via the reaction of arenediazonium salts 68 with cyclopropanols 69. Conducted under
mild conditions in acetonitrile at room temperature, the transformation proceeds within 20 minutes
under blue LED irradiation using Ru(bpy)3Cl₂·6H₂O (5 mol%) as photocatalyst. The protocol
exhibits broad functional group tolerance, excellent regioselectivity, and delivers the desired
pyrazoles in yields of up to 90%. Fluorinated motifs are well represented in both starting
arenediazoniums 68 and the resulting heterocycles 70, appearing as fluoro (F), trifluoromethyl
(CF₃), or pentafluorosulfanyl (SF₅) substituents—underscoring the relevance of this method for
constructing fluorinated pyrazole derivatives with potential medicinal applications.
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Hou et al. (Scheme 24) [157] reported a vi
sible-light-induced chlorotrifluoromethylative
cyclization strategy for synthesizing chlorotri-
fluoromethylated cyclic scaffolds. The method
leverages photogenerated trifluoromethyl radi-
cals to initiate a cascade involving radical addi-
tion, cyclization, and subsequent chlorination.
Employing terminal alkene-derived enynes
65 and trifluoromethanesulfonyl chloride 66,
this protocol delivers regio- and stereoselec-
tive access to pyrrolidines and cyclopentanes
67 bearing trifluoromethyl group, with yields
ranging from 70–75%. Reactions are per-
formed in 1,2-dichloromethane (DCM) under
an argon atmosphere at ambient temperature,
using K₂HPO₄ (5 equiv.) as an additive and
Ru(bpy)3Cl₂ (5 mol%) as photocatalyst under
23 W fluorescent lamp irradiation. The result-
ing trifluoromethylated pyrrolidines are of sig-
nificant biomedical interest and can be further
derivatized via the embedded vinylchloride
functionality, enabling downstream molecular
elaboration.
Scheme 23. Synthesis of fluorinated tetrahydrocarbazoles.
Hou et al. (Scheme 24) [157] reported a visible-light-induced chlorotrifluoromethylative cyclization
strategy for synthesizing chlorotrifluoromethylated cyclic scaffolds. The method leverages
photogenerated trifluoromethyl radicals to initiate a cascade involving radical addition, cyclization,
and subsequent chlorination. Employing terminal alkene-derived enynes 65 and
trifluoromethanesulfonyl chloride 66, this protocol delivers regio- and stereoselective access to
pyrrolidines and cyclopentanes 67 bearing trifluoromethyl group, with yields ranging from 70–75%.
Reactions are performed in 1,2-dichloromethane (DCM) under an argon atmosphere at ambient
temperature, using K₂HPO₄ (5 equiv.) as an additive and Ru(bpy)3Cl₂ (5 mol%) as photocatalyst
under 23 W fluorescent lamp irradiation. The resulting trifluoromethylated pyrrolidines are of
significant biomedical interest and can be further derivatized via the embedded vinylchloride
functionality, enabling downstream molecular elaboration.
Scheme 24. Synthesis of trifluoromethyl-containing pyrrolidine and cyclopentane.
Cardinale et al. (Scheme 25) [158] reported a photocatalytic strategy for synthesizing 1,5-diaryl
pyrazoles 70 via the reaction of arenediazonium salts 68 with cyclopropanols 69. Conducted under
mild conditions in acetonitrile at room temperature, the transformation proceeds within 20 minutes
under blue LED irradiation using Ru(bpy)3Cl₂·6H₂O (5 mol%) as photocatalyst. The protocol
exhibits broad functional group tolerance, excellent regioselectivity, and delivers the desired
pyrazoles in yields of up to 90%. Fluorinated motifs are well represented in both starting
arenediazoniums 68 and the resulting heterocycles 70, appearing as fluoro (F), trifluoromethyl
(CF₃), or pentafluorosulfanyl (SF₅) substituents—underscoring the relevance of this method for
constructing fluorinated pyrazole derivatives with potential medicinal applications.
Scheme 24. Synthesis of trifluoromethyl-containing pyrrolidine and cyclopentane.
Cardinale et al. (Scheme 25) [158] report-
ed a photocatalytic strategy for synthesizing
1,5-diaryl pyrazoles 70 via the reaction of
arenediazonium salts 68 with cyclopropanols
69. Conducted under mild conditions in ace-
tonitrile at room temperature, the transfor-
mation proceeds within 20 minutes under
blue LED irradiation using Ru(bpy)3Cl₂·6H₂O
(5 mol%) as photocatalyst. The protocol exhib-
its broad functional group tolerance, excellent
regioselectivity, and delivers the desired pyra-
zoles in yields of up to 90%. Fluorinated motifs
are well represented in both starting arenedi-
azoniums 68 and the resulting heterocycles 70,
appearing as fluoro (F), trifluoromethyl (CF₃),
or pentafluorosulfanyl (SF₅) substituents—un-
derscoring the relevance of this method for
constructing fluorinated pyrazole derivatives
with potential medicinal applications.
Bromodifluoroacetate, along with its amide
and phosphorus analogs, is a highly versatile
reagent in synthetic organic chemistry due
to its ability to introduce the difluoromethyl
(CF₂) moiety under mild conditions [159].
Notably, its utility in the synthesis of tailor-
made α- [160-162] and β-amino acids [163-
165] is well documented. Under photochem-
ical conditions, bromodifluoroacetate can also
serve as a precursor to reactive intermediates
via radical formation—a reactivity showcased
in the examples that follow.
46 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
Scheme 25. Synthesis of fluorinated 1,5-disubstituted pyrazoles.
Scheme 25. Synthesis of fluorinated 1,5-disubstituted pyrazoles.
Bromodifluoroacetate, along with its amide and phosphorus analogs, is a highly versatile reagent in
synthetic organic chemistry due to its ability to introduce the difluoromethyl (CF₂) moiety under
mild conditions [159]. Notably, its utility in the synthesis of tailor-made α- [160-162] and β-amino
acids [163-165] is well documented. Under photochemical conditions, bromodifluoroacetate can
also serve as a precursor to reactive intermediates via radical formation—a reactivity showcased in
the examples that follow.
Mei et al. (Scheme 26) [166] described an efficient visible-light-promoted cascade reaction for the
synthesis of tetracyclic tetrahydrocarbazoles 73 from alkene-tethered indoles 71 and
bromodifluoroacetate esters 72. The transformation involves the formation of two carbon–carbon
bonds and one carbon–nitrogen bond, proceeding through a reactive tetrahydrocarbazole
intermediate via dual cyclization. Conducted under mild conditions, the protocol accommodates a
broad substrate scope and affords the desired products in yields of up to 84%. Its synthetic utility
was further highlighted through successful gram-scale synthesis and post-reaction reduction of the
tetracyclic framework. The typical reaction is carried out in dimethylformamide (DMF) with
N,N,N',N'-tetramethylethylenediamine (TMEDA) as an additive, employing fac-Ir(ppy)3 as the
photocatalyst under blue LED irradiation. In addition to the difluoromethylene unit introduced by
bromodifluoroacetate esters 72, the products 73 also feature aromatic fluorination on the benzene
ring, enabling tunable fluorine content with relevance to medicinal and biological applications.
Scheme 26. Synthesis of fluorinated tetracyclic tetrahydrocarbazoles.
Mei et al. (Scheme 27) [167] designed a series of indole-derived alkenes 74 and applied them in a
photocatalytic cascade reaction with bromodifluoroacetate esters 72, resulting in the formation of a
previously unreported class of tetracyclic tetrahydro-γ-carboline derivatives 75 in yields of up to
90%. Mechanistic studies indicate that the transformation proceeds via a key tetrahydro-γ-carboline
intermediate formed through sequential cyclization. The reaction exhibits broad substrate tolerance,
offering an efficient and modular approach to constructing tetracyclic tetrahydro-γ-carboline
frameworks. In addition to the difluoromethylene unit introduced by the bromodifluoroacetate
esters, the products also incorporate aromatic fluorine substituents on the benzene ring, enabling the
fine-tuning of fluorine content for applications in medicinal and biological contexts. The reaction is
Scheme 25. Synthesis of fluorinated 1,5-disubstituted pyrazoles.
Bromodifluoroacetate, along with its amide and phosphorus analogs, is a highly versatile reagent in
synthetic organic chemistry due to its ability to introduce the difluoromethyl (CF₂) moiety under
mild conditions [159]. Notably, its utility in the synthesis of tailor-made α- [160-162] and β-amino
acids [163-165] is well documented. Under photochemical conditions, bromodifluoroacetate can
also serve as a precursor to reactive intermediates via radical formation—a reactivity showcased in
the examples that follow.
Mei et al. (Scheme 26) [166] described an efficient visible-light-promoted cascade reaction for the
synthesis of tetracyclic tetrahydrocarbazoles 73 from alkene-tethered indoles 71 and
bromodifluoroacetate esters 72. The transformation involves the formation of two carbon–carbon
bonds and one carbon–nitrogen bond, proceeding through a reactive tetrahydrocarbazole
intermediate via dual cyclization. Conducted under mild conditions, the protocol accommodates a
broad substrate scope and affords the desired products in yields of up to 84%. Its synthetic utility
was further highlighted through successful gram-scale synthesis and post-reaction reduction of the
tetracyclic framework. The typical reaction is carried out in dimethylformamide (DMF) with
N,N,N',N'-tetramethylethylenediamine (TMEDA) as an additive, employing fac-Ir(ppy)3 as the
photocatalyst under blue LED irradiation. In addition to the difluoromethylene unit introduced by
bromodifluoroacetate esters 72, the products 73 also feature aromatic fluorination on the benzene
ring, enabling tunable fluorine content with relevance to medicinal and biological applications.
Scheme 26. Synthesis of fluorinated tetracyclic tetrahydrocarbazoles.
Mei et al. (Scheme 27) [167] designed a series of indole-derived alkenes 74 and applied them in a
photocatalytic cascade reaction with bromodifluoroacetate esters 72, resulting in the formation of a
previously unreported class of tetracyclic tetrahydro-γ-carboline derivatives 75 in yields of up to
90%. Mechanistic studies indicate that the transformation proceeds via a key tetrahydro-γ-carboline
intermediate formed through sequential cyclization. The reaction exhibits broad substrate tolerance,
offering an efficient and modular approach to constructing tetracyclic tetrahydro-γ-carboline
frameworks. In addition to the difluoromethylene unit introduced by the bromodifluoroacetate
esters, the products also incorporate aromatic fluorine substituents on the benzene ring, enabling the
fine-tuning of fluorine content for applications in medicinal and biological contexts. The reaction is
Mei et al. (Scheme 26) [166] described an
efficient visible-light-promoted cascade reac-
tion for the synthesis of tetracyclic tetrahydro-
carbazoles 73 from alkene-tethered indoles 71
and bromodifluoroacetate esters 72. The trans-
formation involves the formation of two car-
bon–carbon bonds and one carbon–nitrogen
bond, proceeding through a reactive tetrahy-
drocarbazole intermediate via dual cyclization.
Conducted under mild conditions, the proto-
col accommodates a broad substrate scope and
affords the desired products in yields of up to
84%. Its synthetic utility was further highlight-
ed through successful gram-scale synthesis
and post-reaction reduction of the tetracyclic
framework. The typical reaction is carried out
in dimethylformamide (DMF) with N,N,N’,N’-
tetramethylethylenediamine (TMEDA) as an
additive, employing fac-Ir(ppy)3 as the photo-
catalyst under blue LED irradiation. In addi-
tion to the difluoromethylene unit introduced
by bromodifluoroacetate esters 72, the prod-
ucts 73 also feature aromatic fluorination on
the benzene ring, enabling tunable fluorine
content with relevance to medicinal and bio-
logical applications.
Scheme 26. Synthesis of fluorinated tetracyclic tetrahydrocarbazoles.
Mei et al. (Scheme 27) [167] designed a se-
ries of indole-derived alkenes 74 and applied
them in a photocatalytic cascade reaction
with bromodifluoroacetate esters 72, result-
ing in the formation of a previously unreport-
ed class of tetracyclic tetrahydro-γ-carboline
derivatives 75 in yields of up to 90%. Mecha-
nistic studies indicate that the transformation
proceeds via a key tetrahydro-γ-carboline in-
termediate formed through sequential cycli-
zation. The reaction exhibits broad substrate
tolerance, offering an efficient and modular
approach to constructing tetracyclic tetrahy-
dro-γ-carboline frameworks. In addition to
47https://ucj.org.ua
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the difluoromethylene unit introduced by the
bromodifluoroacetate esters, the products also
incorporate aromatic fluorine substituents on
the benzene ring, enabling the fine-tuning of
fluorine content for applications in medicinal
and biological contexts. The reaction is typical-
ly performed in dioxane with TMEDA as base,
under a nitrogen atmosphere at room temper-
ature for two hours. Photocatalysis is facilitated
by fac-Ir(ppy)3 under irradiation from a 4.5 W
blue LED source.
Scheme 27. Synthesis of fluorinated tetrahydro-γ-carbolines.
typically performed in dioxane with TMEDA as base, under a nitrogen atmosphere at room
temperature for two hours. Photocatalysis is facilitated by fac-Ir(ppy)3 under irradiation from a 4.5
W blue LED source.
Scheme 27. Synthesis of fluorinated tetrahydro-γ-carbolines.
Zhou et al. (Scheme 28) [168] reported a visible-light-mediated difluoroalkylation of 1-
(allyloxy)-2-(1-arylvinyl)benzenes and 1-(1-arylvinyl)-2-(vinyloxy)benzenes 76 using
bromodifluoroacetate esters 72 to access bis-difluoroalkylated benzoxepines and 2H-chromenes 77
in yields of up to 73%. The transformation proceeds under mild conditions, exhibiting excellent
regioselectivity, broad substrate scope, good functional-group tolerance, and compatibility with
late-stage functionalization. Mechanistic studies suggest that the CF₂CO₂Et radical preferentially
adds to the aryl-adjacent double bond. Reactions are conducted at room temperature in acetonitrile
under an argon atmosphere, employing NaOAc (2 equiv.) to neutralize the liberated hydrogen
bromide. Photocatalysis is facilitated by fac-Ir(ppy)3 under irradiation from a 12 W blue LED
source.
Scheme 28. Preparation of bis-difluoroalkylated benzoxepines and2H-chromenes.
Lian et al. (Scheme 29) [169] reported a photoredox-catalyzed cascade reaction for the synthesis of
fluorinated pyrrolo[1,2-d]benzodiazepine derivatives 79 under mild conditions. The process is
initiated by single-electron transfer (SET) from the excited-state photocatalyst fac-Ir(ppy)3 (2
mol%) to ethyl bromodifluoroacetate 72, generating a reactive radical species that undergoes
regioselective addition to a diverse array of 2-(1H-pyrrol-1-yl)anilines 78. A subsequent SET event
triggers intramolecular amidation, forming the desired tetracyclic scaffold. Reactions are conducted
in dichloromethane at room temperature under an argon atmosphere, with triethylamine as base, and
irradiated using a 23 W compact fluorescent lamp (CFL) over 30 hours. In addition to the
difluoromethylene moiety introduced by reagent 72, the final products feature additional fluorine
substitution, either as monofluoro or trifluoromethyl (CF₃) groups—enhancing their relevance for
medicinal and structural exploration.
typically performed in dioxane with TMEDA as base, under a nitrogen atmosphere at room
temperature for two hours. Photocatalysis is facilitated by fac-Ir(ppy)3 under irradiation from a 4.5
W blue LED source.
Scheme 27. Synthesis of fluorinated tetrahydro-γ-carbolines.
Zhou et al. (Scheme 28) [168] reported a visible-light-mediated difluoroalkylation of 1-
(allyloxy)-2-(1-arylvinyl)benzenes and 1-(1-arylvinyl)-2-(vinyloxy)benzenes 76 using
bromodifluoroacetate esters 72 to access bis-difluoroalkylated benzoxepines and 2H-chromenes 77
in yields of up to 73%. The transformation proceeds under mild conditions, exhibiting excellent
regioselectivity, broad substrate scope, good functional-group tolerance, and compatibility with
late-stage functionalization. Mechanistic studies suggest that the CF₂CO₂Et radical preferentially
adds to the aryl-adjacent double bond. Reactions are conducted at room temperature in acetonitrile
under an argon atmosphere, employing NaOAc (2 equiv.) to neutralize the liberated hydrogen
bromide. Photocatalysis is facilitated by fac-Ir(ppy)3 under irradiation from a 12 W blue LED
source.
Scheme 28. Preparation of bis-difluoroalkylated benzoxepines and2H-chromenes.
Lian et al. (Scheme 29) [169] reported a photoredox-catalyzed cascade reaction for the synthesis of
fluorinated pyrrolo[1,2-d]benzodiazepine derivatives 79 under mild conditions. The process is
initiated by single-electron transfer (SET) from the excited-state photocatalyst fac-Ir(ppy)3 (2
mol%) to ethyl bromodifluoroacetate 72, generating a reactive radical species that undergoes
regioselective addition to a diverse array of 2-(1H-pyrrol-1-yl)anilines 78. A subsequent SET event
triggers intramolecular amidation, forming the desired tetracyclic scaffold. Reactions are conducted
in dichloromethane at room temperature under an argon atmosphere, with triethylamine as base, and
irradiated using a 23 W compact fluorescent lamp (CFL) over 30 hours. In addition to the
difluoromethylene moiety introduced by reagent 72, the final products feature additional fluorine
substitution, either as monofluoro or trifluoromethyl (CF₃) groups—enhancing their relevance for
medicinal and structural exploration.
Zhou et al. (Scheme 28) [168] report-
ed a visible-light-mediated difluoroalkyla-
tion of 1-(allyloxy)-2-(1-arylvinyl)benzenes
and 1-(1-arylvinyl)-2-(vinyloxy)benzenes 76
using bromodifluoroacetate esters 72 to ac-
cess bis-difluoroalkylated benzoxepines and
2H-chromenes 77 in yields of up to 73%. The
transformation proceeds under mild condi
tions, exhibiting excellent regioselectivity,
broad substrate scope, good functional-group
tolerance, and compatibility with late-stage
functionalization. Mechanistic studies suggest
that the CF₂CO₂Et radical preferentially adds
to the aryl-adjacent double bond. Reactions
are conducted at room temperature in acetoni-
trile under an argon atmosphere, employing
NaOAc (2 equiv.) to neutralize the liberated
hydrogen bromide. Photocatalysis is facilitated
by fac-Ir(ppy)3 under irradiation from a 12 W
blue LED source.
Scheme 28. Preparation of bis-difluoroalkylated benzoxepines and2H-chromenes.
Lian et al. (Scheme 29) [169] reported a
photoredox-catalyzed cascade reaction for the
synthesis of fluorinated pyrrolo[1,2-d]benzo-
diazepine derivatives 79 under mild condi-
tions. The process is initiated by single-elec-
tron transfer (SET) from the excited-state
photocatalyst fac-Ir(ppy)3 (2 mol%) to ethyl
bromodifluoroacetate 72, generating a reactive
radical species that undergoes regioselective
addition to a diverse array of 2-(1H-pyrrol-1-
yl)anilines 78. A subsequent SET event triggers
intramolecular amidation, forming the desired
48 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
tetracyclic scaffold. Reactions are conducted in
dichloromethane at room temperature under
an argon atmosphere, with triethylamine as
base, and irradiated using a 23 W compact flu-
orescent lamp (CFL) over 30 hours. In addition
to the difluoromethylene moiety introduced by
reagent 72, the final products feature addition-
al fluorine substitution, either as monofluoro
or trifluoromethyl (CF₃) groups—enhancing
their relevance for medicinal and structural
exploration.
Scheme 29. Preparation of fluorinated pyrrolo[1,2-d]benzodiazepine.
Scheme 29. Preparation of fluorinated pyrrolo[1,2-d]benzodiazepine.
Hydroxanthones have garnered significant attention for their roles in organic synthesis and
medicinal chemistry, yet efficient methods for their construction remain limited. Wang et al.
(Scheme 30) [170] reported a photoredox-enabled synthesis of tetrahydroxanthone derivatives 82
via radical cyclization of chromone-tethered alkenes 80 and bromodifluoroacetamide or
bromodifluoroacetate reagents 81. The transformation proceeds under visible-light irradiation
through the generation of either difluoroacetate radicals or alkene radical cations, facilitated by fac-
Ir(ppy)3 or [Ru(bpy)3](PF₆)₂ as photocatalysts. Conducted in tetrahydrofuran (THF) at room
temperature under an argon atmosphere, the reaction employs K₃PO₄ as base and a 4.5 W blue LED
light source. This protocol provides access to functionalized tetrahydroxanthones in yields of up to
85%, showcasing broad substrate scope and synthetic utility. Beyond enabling efficient construction
from readily available building blocks, this strategy enriches the chemistry of heteroarene-tethered
alkenes and expands the toolkit for designing fluorinated polycyclic scaffolds.
Scheme 30. Synthesis of fluorinated tetrahydroxanthones.
Stefanoni and Wilhelm (Scheme 31) [171] reported a mild, scalable, and highly chemoselective
photocatalytic method for the direct functionalization of indolizines 83 using N-
[(trifluoromethyl)thio]saccharin 84 as a trifluoromethylthiolation reagent. The reaction proceeds
smoothly in acetone at room temperature under an argon atmosphere, employing [Ru(bpy)3](PF₆)₂
as the photocatalyst and 3 W blue LEDs (455 nm) for 3 hours. The protocol exhibits broad
functional-group tolerance and affords the SCF₃-substituted products 85 in yields of approximately
70%. Incorporation of the trifluoromethylthio (SCF₃) group is particularly valuable in drug
development, as it enhances the metabolic stability and membrane permeability of bioactive
compounds.
Scheme 31. Synthesis of (trifluoromethyl)thio-modified indolizines.
Scheme 29. Preparation of fluorinated pyrrolo[1,2-d]benzodiazepine.
Hydroxanthones have garnered significant attention for their roles in organic synthesis and
medicinal chemistry, yet efficient methods for their construction remain limited. Wang et al.
(Scheme 30) [170] reported a photoredox-enabled synthesis of tetrahydroxanthone derivatives 82
via radical cyclization of chromone-tethered alkenes 80 and bromodifluoroacetamide or
bromodifluoroacetate reagents 81. The transformation proceeds under visible-light irradiation
through the generation of either difluoroacetate radicals or alkene radical cations, facilitated by fac-
Ir(ppy)3 or [Ru(bpy)3](PF₆)₂ as photocatalysts. Conducted in tetrahydrofuran (THF) at room
temperature under an argon atmosphere, the reaction employs K₃PO₄ as base and a 4.5 W blue LED
light source. This protocol provides access to functionalized tetrahydroxanthones in yields of up to
85%, showcasing broad substrate scope and synthetic utility. Beyond enabling efficient construction
from readily available building blocks, this strategy enriches the chemistry of heteroarene-tethered
alkenes and expands the toolkit for designing fluorinated polycyclic scaffolds.
Scheme 30. Synthesis of fluorinated tetrahydroxanthones.
Stefanoni and Wilhelm (Scheme 31) [171] reported a mild, scalable, and highly chemoselective
photocatalytic method for the direct functionalization of indolizines 83 using N-
[(trifluoromethyl)thio]saccharin 84 as a trifluoromethylthiolation reagent. The reaction proceeds
smoothly in acetone at room temperature under an argon atmosphere, employing [Ru(bpy)3](PF₆)₂
as the photocatalyst and 3 W blue LEDs (455 nm) for 3 hours. The protocol exhibits broad
functional-group tolerance and affords the SCF₃-substituted products 85 in yields of approximately
70%. Incorporation of the trifluoromethylthio (SCF₃) group is particularly valuable in drug
development, as it enhances the metabolic stability and membrane permeability of bioactive
compounds.
Scheme 31. Synthesis of (trifluoromethyl)thio-modified indolizines.
Hydroxanthones have garnered significant
attention for their roles in organic synthesis
and medicinal chemistry, yet efficient methods
for their construction remain limited. Wang
et al. (Scheme 30) [170] reported a photore-
dox-enabled synthesis of tetrahydroxanthone
derivatives 82 via radical cyclization of chro-
mone-tethered alkenes 80 and bromodifluo-
roacetamide or bromodifluoroacetate reagents
81. The transformation proceeds under visi-
ble-light irradiation through the generation
of either difluoroacetate radicals or alkene
radical cations, facilitated by fac-Ir(ppy)3 or
[Ru(bpy)3](PF₆)₂ as photocatalysts. Conducted
in tetrahydrofuran (THF) at room tempera-
ture under an argon atmosphere, the reaction
employs K₃PO₄ as base and a 4.5 W blue LED
light source. This protocol provides access to
functionalized tetrahydroxanthones in yields
of up to 85%, showcasing broad substrate scope
and synthetic utility. Beyond enabling efficient
construction from readily available building
blocks, this strategy enriches the chemistry
of heteroarene-tethered alkenes and expands
the toolkit for designing fluorinated polycyclic
scaffolds.
Scheme 30. Synthesis of fluorinated tetrahydroxanthones.
Stefanoni and Wilhelm (Scheme 31) [171]
reported a mild, scalable, and highly chemo
selective photocatalytic method for the di-
rect functionalization of indolizines 83 using
49https://ucj.org.ua
Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
N-[(trifluoromethyl)thio]saccharin 84 as a tri-
fluoromethylthiolation reagent. The reaction
proceeds smoothly in acetone at room temper-
ature under an argon atmosphere, employing
[Ru(bpy)3](PF₆)₂ as the photocatalyst and 3 W
blue LEDs (455 nm) for 3 hours. The proto-
col exhibits broad functional-group tolerance
and affords the SCF₃-substituted products 85
in yields of approximately 70%. Incorpora-
tion of the trifluoromethylthio (SCF₃) group is
particularly valuable in drug development, as
it enhances the metabolic stability and mem-
brane permeability of bioactive compounds.
Scheme 29. Preparation of fluorinated pyrrolo[1,2-d]benzodiazepine.
Hydroxanthones have garnered significant attention for their roles in organic synthesis and
medicinal chemistry, yet efficient methods for their construction remain limited. Wang et al.
(Scheme 30) [170] reported a photoredox-enabled synthesis of tetrahydroxanthone derivatives 82
via radical cyclization of chromone-tethered alkenes 80 and bromodifluoroacetamide or
bromodifluoroacetate reagents 81. The transformation proceeds under visible-light irradiation
through the generation of either difluoroacetate radicals or alkene radical cations, facilitated by fac-
Ir(ppy)3 or [Ru(bpy)3](PF₆)₂ as photocatalysts. Conducted in tetrahydrofuran (THF) at room
temperature under an argon atmosphere, the reaction employs K₃PO₄ as base and a 4.5 W blue LED
light source. This protocol provides access to functionalized tetrahydroxanthones in yields of up to
85%, showcasing broad substrate scope and synthetic utility. Beyond enabling efficient construction
from readily available building blocks, this strategy enriches the chemistry of heteroarene-tethered
alkenes and expands the toolkit for designing fluorinated polycyclic scaffolds.
Scheme 30. Synthesis of fluorinated tetrahydroxanthones.
Stefanoni and Wilhelm (Scheme 31) [171] reported a mild, scalable, and highly chemoselective
photocatalytic method for the direct functionalization of indolizines 83 using N-
[(trifluoromethyl)thio]saccharin 84 as a trifluoromethylthiolation reagent. The reaction proceeds
smoothly in acetone at room temperature under an argon atmosphere, employing [Ru(bpy)3](PF₆)₂
as the photocatalyst and 3 W blue LEDs (455 nm) for 3 hours. The protocol exhibits broad
functional-group tolerance and affords the SCF₃-substituted products 85 in yields of approximately
70%. Incorporation of the trifluoromethylthio (SCF₃) group is particularly valuable in drug
development, as it enhances the metabolic stability and membrane permeability of bioactive
compounds.
Scheme 31. Synthesis of (trifluoromethyl)thio-modified indolizines. Scheme 31. Synthesis of (trifluoromethyl)thio-modified indolizines.
Fluorine-containing benzoimidazoles and
quinazolines [172, 173] exhibit a wide range
of properties valuable to medicinal chemistry
and molecular design. In a notable contribu-
tion, Jiang et al. [174] (Scheme 32) reported a
visible-light photoredox-catalyzed radical cas-
cade cyclization involving 2-phenyl-1H-ben-
zo[d]imidazole-1-carbonitriles 86 and simple
ethers. This strategy enables sequential inert
C(sp³)-H and C(sp²)-H functionalizations,
initiated by the intermolecular addition of ox-
yalkyl radicals to N-cyano groups. The process
proceeds via in situ generation and intramolec-
ular cyclization of iminyl radicals, incorporat-
ing C-2 aryl substituents. The transformation
affords tetracyclic benzo[4,5]imidazo[1,2-c]
quinazolines 87 in 65–86% yield under am-
bient conditions. Key reaction parameters in-
clude 2 equivalents of di-tert-butyl peroxide
(DTBP) and irradiation with 25 W blue LEDs
for 14 hours, using Ir[dFppy]2(dtbbpy)]PF₆
(1 mol%) as the photoredox catalyst. Fluorina-
tion is represented by the presence of aromatic
fluorine atoms and trifluoromethyl groups, en-
hancing the structural diversity and potential
bioactivity of the products.
Scheme 32. Synthesis of benzo[4,5]imidazo[1,2-c]quinazolines.
Fluorine-containing benzoimidazoles and quinazolines [172, 173] exhibit a wide range of properties
valuable to medicinal chemistry and molecular design. In a notable contribution, Jiang et al. [174]
(Scheme 32) reported a visible-light photoredox-catalyzed radical cascade cyclization involving 2-
phenyl-1H-benzo[d]imidazole-1-carbonitriles 86 and simple ethers. This strategy enables sequential
inert C(sp³)-H and C(sp²)-H functionalizations, initiated by the intermolecular addition of oxyalkyl
radicals to N-cyano groups. The process proceeds via in situ generation and intramolecular
cyclization of iminyl radicals, incorporating C-2 aryl substituents. The transformation affords
tetracyclic benzo[4,5]imidazo[1,2-c]quinazolines 87 in 65–86% yield under ambient conditions.
Key reaction parameters include 2 equivalents of di-tert-butyl peroxide (DTBP) and irradiation with
25 W blue LEDs for 14 hours, using Ir[dFppy]2(dtbbpy)]PF₆ (1 mol%) as the photoredox catalyst.
Fluorination is represented by the presence of aromatic fluorine atoms and trifluoromethyl groups,
enhancing the structural diversity and potential bioactivity of the products.
Scheme 32. Synthesis of benzo[4,5]imidazo[1,2-c]quinazolines.
Zhang et al. (Scheme 33) [175] reported a visible-light-induced ring-opening C(sp³)–C bond
coupling between quinoxalin-2(1H)-ones 88 and cyclobutanone oxime esters to access cyanoalkyl-
substituted quinoxalin-2(1H)-ones 89. The transformation proceeds under sunlight or blue LED
irradiation at room temperature, without requiring additional additives, and delivers a range of
functionalized alkylnitrile derivatives in moderate to excellent yields. The reaction protocol is
operationally simple, displays broad functional-group tolerance, and is amenable to scale-up.
Mechanistic investigations revealed the involvement of a cyanoalkyl radical intermediate in the key
bond-forming step. Reactions are conducted in dichloromethane under an argon atmosphere,
employing fac-Ir(ppy)3 as the photocatalyst and 6 W blue LEDs as the light source. Fluorinated
products 89, featuring aromatic fluorine atoms on the benzene ring, were obtained in isolated yields
ranging from 30% to 67%.
Scheme 33. Synthesis of cyanoalkyl-substituted quinoxalin-2(1H)-ones.
Mao et al. (Scheme 34) [176] developed an efficient and straightforward visible-light-mediated
tandem difluoromethylation–cyclization of alkenyl aldehydes 90 using the air-stable and readily
accessible reagent [Ph₃PCF₂H]⁺Br⁻ as a source of the CF₂H group. This transformation enables the
synthesis of CF₂H-functionalized chroman-4-one scaffolds and related heterocycles—including
chromen-4-ones, quinolin-4(1H)-ones, and thiochromen-4-ones 91—with moderate to excellent
yields (30–90%) and outstanding chemoselectivity under mild conditions. The reaction is typically
performed in DMSO at ambient temperature, employing 2,6-lutidine to scavenge the liberated HBr.
Zhang et al. (Scheme 33) [175] reported a
visible-light-induced ring-opening C(sp³)–C
bond coupling between quinoxalin-2(1H)-ones
88 and cyclobutanone oxime esters to access
50 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
cyanoalkyl-substituted quinoxalin-2(1H)-ones
89. The transformation proceeds under sun-
light or blue LED irradiation at room temper-
ature, without requiring additional additives,
and delivers a range of functionalized alkylni-
trile derivatives in moderate to excellent yields.
The reaction protocol is operationally simple,
displays broad functional-group tolerance, and
is amenable to scale-up. Mechanistic investiga-
tions revealed the involvement of a cyanoalkyl
radical intermediate in the key bond-form-
ing step. Reactions are conducted in dichlo-
romethane under an argon atmosphere, em-
ploying fac-Ir(ppy)3 as the photocatalyst and
6 W blue LEDs as the light source. Fluorinated
products 89, featuring aromatic fluorine atoms
on the benzene ring, were obtained in isolated
yields ranging from 30% to 67%.
Fluorine-containing benzoimidazoles and quinazolines [172, 173] exhibit a wide range of properties
valuable to medicinal chemistry and molecular design. In a notable contribution, Jiang et al. [174]
(Scheme 32) reported a visible-light photoredox-catalyzed radical cascade cyclization involving 2-
phenyl-1H-benzo[d]imidazole-1-carbonitriles 86 and simple ethers. This strategy enables sequential
inert C(sp³)-H and C(sp²)-H functionalizations, initiated by the intermolecular addition of oxyalkyl
radicals to N-cyano groups. The process proceeds via in situ generation and intramolecular
cyclization of iminyl radicals, incorporating C-2 aryl substituents. The transformation affords
tetracyclic benzo[4,5]imidazo[1,2-c]quinazolines 87 in 65–86% yield under ambient conditions.
Key reaction parameters include 2 equivalents of di-tert-butyl peroxide (DTBP) and irradiation with
25 W blue LEDs for 14 hours, using Ir[dFppy]2(dtbbpy)]PF₆ (1 mol%) as the photoredox catalyst.
Fluorination is represented by the presence of aromatic fluorine atoms and trifluoromethyl groups,
enhancing the structural diversity and potential bioactivity of the products.
Scheme 32. Synthesis of benzo[4,5]imidazo[1,2-c]quinazolines.
Zhang et al. (Scheme 33) [175] reported a visible-light-induced ring-opening C(sp³)–C bond
coupling between quinoxalin-2(1H)-ones 88 and cyclobutanone oxime esters to access cyanoalkyl-
substituted quinoxalin-2(1H)-ones 89. The transformation proceeds under sunlight or blue LED
irradiation at room temperature, without requiring additional additives, and delivers a range of
functionalized alkylnitrile derivatives in moderate to excellent yields. The reaction protocol is
operationally simple, displays broad functional-group tolerance, and is amenable to scale-up.
Mechanistic investigations revealed the involvement of a cyanoalkyl radical intermediate in the key
bond-forming step. Reactions are conducted in dichloromethane under an argon atmosphere,
employing fac-Ir(ppy)3 as the photocatalyst and 6 W blue LEDs as the light source. Fluorinated
products 89, featuring aromatic fluorine atoms on the benzene ring, were obtained in isolated yields
ranging from 30% to 67%.
Scheme 33. Synthesis of cyanoalkyl-substituted quinoxalin-2(1H)-ones.
Mao et al. (Scheme 34) [176] developed an efficient and straightforward visible-light-mediated
tandem difluoromethylation–cyclization of alkenyl aldehydes 90 using the air-stable and readily
accessible reagent [Ph₃PCF₂H]⁺Br⁻ as a source of the CF₂H group. This transformation enables the
synthesis of CF₂H-functionalized chroman-4-one scaffolds and related heterocycles—including
chromen-4-ones, quinolin-4(1H)-ones, and thiochromen-4-ones 91—with moderate to excellent
yields (30–90%) and outstanding chemoselectivity under mild conditions. The reaction is typically
performed in DMSO at ambient temperature, employing 2,6-lutidine to scavenge the liberated HBr.
Scheme 33. Synthesis of cyanoalkyl-substituted quinoxalin-2(1H)-ones.
Mao et al. (Scheme 34) [176] developed an ef-
ficient and straightforward visible-light-medi-
ated tandem difluoromethylation–cyclization
of alkenyl aldehydes 90 using the air-stable and
readily accessible reagent [Ph₃PCF₂H]⁺Br⁻ as a
source of the CF₂H group. This transformation
enables the synthesis of CF₂H-functionalized
chroman-4-one scaffolds and related heter-
ocycles—including chromen-4-ones, quino-
lin-4(1H)-ones, and thiochromen-4-ones 91—
with moderate to excellent yields (30–90%)
and outstanding chemoselectivity under mild
conditions. The reaction is typically performed
in DMSO at ambient temperature, employ-
ing 2,6-lutidine to scavenge the liberated HBr.
Photochemical activation is achieved using
fac-Ir(ppy)3 (2 mol%) under blue LED irradi-
ation for 24 hours. In addition to introducing
an aliphatic difluoromethyl group, the result-
ing heterocyclic products 91 frequently incor-
porate aromatic fluorination on the benzene
ring. This dual fluorine pattern facilitates the
generation of compound libraries with diverse
fluorine substitution profiles—highly relevant
for molecular design and medicinal chemistry
applications.
Photochemical activation is achieved using fac-Ir(ppy)3 (2 mol%) under blue LED irradiation for 24
hours. In addition to introducing an aliphatic difluoromethyl group, the resulting heterocyclic
products 91 frequently incorporate aromatic fluorination on the benzene ring. This dual fluorine
pattern facilitates the generation of compound libraries with diverse fluorine substitution profiles—
highly relevant for molecular design and medicinal chemistry applications.
Scheme 34. Synthesis of difluoromethyl-substituted chromen-4-ones, quinolin-4(1H)-ones and
thiochromen-4-ones.
Meng et al. (Scheme 35) [177] reported a visible-light-induced fluoroalkylation–cycloisomerization
cascade involving ene-substrates 92 and either ethyl iododifluoroacetate or perfluoroalkyl iodides
93. This transformation affords fluorinated pyrrolidine derivatives 94 in moderate to excellent
yields (23–93%) under mild conditions, while demonstrating broad functional group tolerance.
Mechanistic studies suggest a radical chain pathway, initiated under visible-light irradiation, as
central to the formation of the heterocyclic scaffolds. Reactions are typically conducted in dioxane
under an argon atmosphere at room temperature, using fac-Ir(ppy)3 (5 mol%) as the photocatalyst
and 30 W blue LEDs as the irradiation source over 12 hours. In addition to the incorporation of
aliphatic fluoroacetic or perfluoroalkyl chains, the products also feature aromatic fluorination on the
benzene ring, resulting in a dual fluorine motif. This structural versatility enables the design of
compound libraries with varied fluorine substitution patterns—highly relevant for medicinal
chemistry and molecular property tuning. Beyond their bioactive potential, chiral pyrrolidine
frameworks are recognized as privileged scaffolds in asymmetric synthesis [178–180], further
underscoring the synthetic utility of this methodology.
Scheme 35. Synthesis of fluorinated pyrrolidines.
Liang et al. (Scheme 36) [181] reported a visible-light-driven, photoredox-catalyzed radical
cyclization between isocyanides 92 and thiols 93, furnishing 2-thioquinoline derivatives 94 in an
efficient and regioselective manner from readily available starting materials. Mechanistic studies
suggest that the reaction may proceed via the in situ generation of either a sulfide radical cation or
an α-thioalkyl radical, which undergoes addition to the isocyanide moiety, followed by
intramolecular cyclization and/or intermolecular nucleophilic substitution to form the quinoline
core. Reactions are performed in tetrahydrofuran (THF) with 2 equivalents of 1,8-
diazabicyclo[5.4.0]undec-7-ene (DBU) as base, under ambient conditions. Photochemical activation
Scheme 34. Synthesis of difluoromethyl-substituted chromen-4-ones, quinolin-4(1H)-ones
and thiochromen-4-ones.
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Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
Meng et al. (Scheme 35) [177] reported a
visible-light-induced fluoroalkylation–cyclo
isomerization cascade involving ene-sub-
strates 92 and either ethyl iododifluoroacetate
or perfluoroalkyl iodides 93. This transforma-
tion affords fluorinated pyrrolidine derivatives
94 in moderate to excellent yields (23–93%)
under mild conditions, while demonstrating
broad functional group tolerance. Mechanistic
studies suggest a radical chain pathway, initi-
ated under visible-light irradiation, as central
to the formation of the heterocyclic scaffolds.
Reactions are typically conducted in dioxane
under an argon atmosphere at room tempera-
ture, using fac-Ir(ppy)3 (5 mol%) as the photo-
catalyst and 30 W blue LEDs as the irradiation
source over 12 hours. In addition to the incor-
poration of aliphatic fluoroacetic or perfluoro-
alkyl chains, the products also feature aromatic
fluorination on the benzene ring, resulting in a
dual fluorine motif. This structural versatility
enables the design of compound libraries with
varied fluorine substitution patterns—highly
relevant for medicinal chemistry and molec-
ular property tuning. Beyond their bioactive
potential, chiral pyrrolidine frameworks are
recognized as privileged scaffolds in asymmet-
ric synthesis [178–180], further underscoring
the synthetic utility of this methodology.
Photochemical activation is achieved using fac-Ir(ppy)3 (2 mol%) under blue LED irradiation for 24
hours. In addition to introducing an aliphatic difluoromethyl group, the resulting heterocyclic
products 91 frequently incorporate aromatic fluorination on the benzene ring. This dual fluorine
pattern facilitates the generation of compound libraries with diverse fluorine substitution profiles—
highly relevant for molecular design and medicinal chemistry applications.
Scheme 34. Synthesis of difluoromethyl-substituted chromen-4-ones, quinolin-4(1H)-ones and
thiochromen-4-ones.
Meng et al. (Scheme 35) [177] reported a visible-light-induced fluoroalkylation–cycloisomerization
cascade involving ene-substrates 92 and either ethyl iododifluoroacetate or perfluoroalkyl iodides
93. This transformation affords fluorinated pyrrolidine derivatives 94 in moderate to excellent
yields (23–93%) under mild conditions, while demonstrating broad functional group tolerance.
Mechanistic studies suggest a radical chain pathway, initiated under visible-light irradiation, as
central to the formation of the heterocyclic scaffolds. Reactions are typically conducted in dioxane
under an argon atmosphere at room temperature, using fac-Ir(ppy)3 (5 mol%) as the photocatalyst
and 30 W blue LEDs as the irradiation source over 12 hours. In addition to the incorporation of
aliphatic fluoroacetic or perfluoroalkyl chains, the products also feature aromatic fluorination on the
benzene ring, resulting in a dual fluorine motif. This structural versatility enables the design of
compound libraries with varied fluorine substitution patterns—highly relevant for medicinal
chemistry and molecular property tuning. Beyond their bioactive potential, chiral pyrrolidine
frameworks are recognized as privileged scaffolds in asymmetric synthesis [178–180], further
underscoring the synthetic utility of this methodology.
Scheme 35. Synthesis of fluorinated pyrrolidines.
Liang et al. (Scheme 36) [181] reported a visible-light-driven, photoredox-catalyzed radical
cyclization between isocyanides 92 and thiols 93, furnishing 2-thioquinoline derivatives 94 in an
efficient and regioselective manner from readily available starting materials. Mechanistic studies
suggest that the reaction may proceed via the in situ generation of either a sulfide radical cation or
an α-thioalkyl radical, which undergoes addition to the isocyanide moiety, followed by
intramolecular cyclization and/or intermolecular nucleophilic substitution to form the quinoline
core. Reactions are performed in tetrahydrofuran (THF) with 2 equivalents of 1,8-
diazabicyclo[5.4.0]undec-7-ene (DBU) as base, under ambient conditions. Photochemical activation
Scheme 35. Synthesis of fluorinated pyrrolidines.
Liang et al. (Scheme 36) [181] reported
a visible-light-driven, photoredox-catalyzed
radical cyclization between isocyanides 92 and
thiols 93, furnishing 2-thioquinoline deriva-
tives 94 in an efficient and regioselective man-
ner from readily available starting materials.
Mechanistic studies suggest that the reaction
may proceed via the in situ generation of either
a sulfide radical cation or an α-thioalkyl ra
dical, which undergoes addition to the isocya-
nide moiety, followed by intramolecular cycli-
zation and/or intermolecular nucleophilic sub-
stitution to form the quinoline core. Reactions
are performed in tetrahydrofuran (THF) with
2 equivalents of 1,8-diazabicyclo[5.4.0]undec-
7-ene (DBU) as base, under ambient condi-
tions. Photochemical activation is achieved
using Ru(bpy)3(PF₆)2 (5 mol%) as the photo-
catalyst and blue LED irradiation, with reac-
tion times ranging from 16 to 32 hours. The
methodology delivers 2-thioquinoline prod-
ucts 94 in yields of 42–97%, depending on sub-
strate variation. Notably, both the isocyanide
precursors and the final products feature mo-
no-fluorine substitution on the benzene ring,
contributing to the structural diversity and po-
tential utility of this protocol in fluorine-rich
heterocyclic library construction.
52 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
Scheme 36. Synthesis of 2-thioquinolines.
is achieved using Ru(bpy)3(PF₆)2 (5 mol%) as the photocatalyst and blue LED irradiation, with
reaction times ranging from 16 to 32 hours. The methodology delivers 2-thioquinoline products 94
in yields of 42–97%, depending on substrate variation. Notably, both the isocyanide precursors and
the final products feature mono-fluorine substitution on the benzene ring, contributing to the
structural diversity and potential utility of this protocol in fluorine-rich heterocyclic library
construction.
Scheme 36. Synthesis of 2-thioquinolines.
Liu et al. (Scheme 37) [182] disclosed a visible-light-promoted strategy for the synthesis of α-
trifluoromethylamines 97 and N-trifluoroethylamine derivatives 98 via C,N-selective
heteroarylation of N-trifluoroethyl hydroxylamine reagents 96 with quinoxalin-2(1H)-ones 95 under
ambient conditions. The reaction’s chemoselectivity—favoring either trifluoroalkylation or N-
trifluoroethylamination—is readily modulated by the structural design of the hydroxylamine
substrate. In particular, the protecting group on the nitrogen atom plays a pivotal role by governing
the 1,2-hydrogen shift of the in situ-generated N-trifluoroethyl radical. This methodology features
mild reaction conditions, operational simplicity, high selectivity, and broad functional group
tolerance. More importantly, the resulting trifluoroalkylated products can be efficiently elaborated
into diverse analogs with promising applications in pharmaceutical development. Reactions are
conducted in acetonitrile with K₃PO₄ as additive, using fac-Ir(ppy)3 (2 mol%) as the photocatalyst
under 24 W purple LED irradiation for 36 hours. Products 97 and 98 are isolated in yields of up to
97%. Beyond the incorporation of an aliphatic trifluoromethyl group, the synthesized heterocyclic
amine derivatives also display aromatic fluorination, enabling access to compound libraries with
varied fluorine substitution patterns—a feature of high relevance for medicinal chemistry and
biological profiling.
Scheme 37. Synthesis of fluorinated quinoxalin-2(1H)-ones.
It is worth noting that the α-trifluoromethyl amino compounds discussed above can be conveniently
accessed from corresponding aldehydes and ketones via a biomimetic transamination pathway [183-
185], commonly referred to as a [1,3]-proton shift reaction [186-188]. Specifically, 2,2,2-
trifluoroethylamine, employed in reagent 96, can be synthesized through a double [1,3]-proton shift
is achieved using Ru(bpy)3(PF₆)2 (5 mol%) as the photocatalyst and blue LED irradiation, with
reaction times ranging from 16 to 32 hours. The methodology delivers 2-thioquinoline products 94
in yields of 42–97%, depending on substrate variation. Notably, both the isocyanide precursors and
the final products feature mono-fluorine substitution on the benzene ring, contributing to the
structural diversity and potential utility of this protocol in fluorine-rich heterocyclic library
construction.
Scheme 36. Synthesis of 2-thioquinolines.
Liu et al. (Scheme 37) [182] disclosed a visible-light-promoted strategy for the synthesis of α-
trifluoromethylamines 97 and N-trifluoroethylamine derivatives 98 via C,N-selective
heteroarylation of N-trifluoroethyl hydroxylamine reagents 96 with quinoxalin-2(1H)-ones 95 under
ambient conditions. The reaction’s chemoselectivity—favoring either trifluoroalkylation or N-
trifluoroethylamination—is readily modulated by the structural design of the hydroxylamine
substrate. In particular, the protecting group on the nitrogen atom plays a pivotal role by governing
the 1,2-hydrogen shift of the in situ-generated N-trifluoroethyl radical. This methodology features
mild reaction conditions, operational simplicity, high selectivity, and broad functional group
tolerance. More importantly, the resulting trifluoroalkylated products can be efficiently elaborated
into diverse analogs with promising applications in pharmaceutical development. Reactions are
conducted in acetonitrile with K₃PO₄ as additive, using fac-Ir(ppy)3 (2 mol%) as the photocatalyst
under 24 W purple LED irradiation for 36 hours. Products 97 and 98 are isolated in yields of up to
97%. Beyond the incorporation of an aliphatic trifluoromethyl group, the synthesized heterocyclic
amine derivatives also display aromatic fluorination, enabling access to compound libraries with
varied fluorine substitution patterns—a feature of high relevance for medicinal chemistry and
biological profiling.
Scheme 37. Synthesis of fluorinated quinoxalin-2(1H)-ones.
It is worth noting that the α-trifluoromethyl amino compounds discussed above can be conveniently
accessed from corresponding aldehydes and ketones via a biomimetic transamination pathway [183-
185], commonly referred to as a [1,3]-proton shift reaction [186-188]. Specifically, 2,2,2-
trifluoroethylamine, employed in reagent 96, can be synthesized through a double [1,3]-proton shift
Liu et al. (Scheme 37) [182] disclosed a vi
sible-light-promoted strategy for the synthesis
of α-trifluoromethylamines 97 and N-trifluo-
roethylamine derivatives 98 via C,N-selective
heteroarylation of N-trifluoroethyl hydroxy-
lamine reagents 96 with quinoxalin-2(1H)-ones
95 under ambient conditions. The reaction’s
chemoselectivity—favoring either trifluoro-
alkylation or N-trifluoroethylamination—is
readily modulated by the structural design of
the hydroxylamine substrate. In particular, the
protecting group on the nitrogen atom plays
a pivotal role by governing the 1,2-hydrogen
shift of the in situ-generated N-trifluoroethyl
radical. This methodology features mild reac-
tion conditions, operational simplicity, high
selectivity, and broad functional group tole
rance. More importantly, the resulting trifluo-
roalkylated products can be efficiently elabo
rated into diverse analogs with promising
applications in pharmaceutical development.
Reactions are conducted in acetonitrile with
K₃PO₄ as additive, using fac-Ir(ppy)3 (2 mol%)
as the photocatalyst under 24 W purple LED
irradiation for 36 hours. Products 97 and 98
are isolated in yields of up to 97%. Beyond the
incorporation of an aliphatic trifluoromethyl
group, the synthesized heterocyclic amine de-
rivatives also display aromatic fluorination,
enabling access to compound libraries with
varied fluorine substitution patterns—a feature
of high relevance for medicinal chemistry and
biological profiling.
Scheme 37. Synthesis of fluorinated quinoxalin-2(1H)-ones.
53https://ucj.org.ua
Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
It is worth noting that the α-trifluorome-
thyl amino compounds discussed above can
be conveniently accessed from correspond-
ing aldehydes and ketones via a biomimetic
transamination pathway [183-185], common-
ly referred to as a [1,3]-proton shift reaction
[186-188]. Specifically, 2,2,2-trifluoroethyl-
amine, employed in reagent 96, can be synthe
sized through a double [1,3]-proton shift se-
quence starting from trifluoroacetic acid and
benzylamine, as illustrated in Scheme 38 [189].
Scheme 38. Synthesis of 2,2,2-trifluoroethylamine via [1,3]-proton shift reaction.
sequence starting from trifluoroacetic acid and benzylamine, as illustrated in Scheme 38 [189].
Scheme 38. Synthesis of 2,2,2-trifluoroethylamine via [1,3]-proton shift reaction.
Coumarin (2H-1-benzopyran-2-one) and its derivatives exhibit a broad spectrum of
pharmacological activities, including anti-inflammatory, antibacterial, antiviral, antioxidant,
antithrombotic, anti-Alzheimer, and anticancer properties [190]. In this context, Tan et al. (Scheme
39) [191] reported a visible-light-induced, photoredox-catalyzed tandem radical addition/cyclization
of 2-alkenylphenols 99 with carbon tetrabromide (CBr₄) to access a variety of 4-arylcoumarins 100
in a one-pot fashion. The reaction proceeds under mild, redox-neutral conditions and demonstrates
good functional-group tolerance, operational simplicity, and scalability. Preliminary mechanistic
studies confirm the radical nature of the process and highlight the essential role of water as an
additive. The transformation is typically conducted in CH₂Cl₂ at ambient temperature with water (5
equiv.) and K₂CO₃ (1.5 equiv.), using fac-Ir(ppy)3 (2 mol%) as photocatalyst and 7 W blue LEDs for
irradiation. The desired coumarin derivatives 100 are isolated in yields ranging from 52% to 95%.
Importantly, fluorination in the final products 100 may be introduced on both aromatic rings, either
as monofluorinated substituents or in combination with trifluoromethyl groups, offering
considerable structural diversity. This enables the design of fluorinated coumarin derivatives with
enhanced medicinal relevance and tunable physicochemical profiles.
Scheme 39. Synthesis of fluorinated 4-arylcoumarins.
Fluorinated indoles are widely recognized as valuable end products due to their potent bioactivity.
However, they also serve as versatile synthetic intermediates for accessing more complex molecular
architectures with desirable biological and physicochemical properties [192]. In this context, Wu et
al. (Scheme 40) [193] developed a visible-light-driven oxidative cyclization protocol utilizing
fluorinated 3-alkenylindoles 101 and styrene 102 to construct carbazole derivatives 103. The
transformation is enabled by Ir(dtbbpy)(ppy)2PF₆ (2 mol%) under aerobic conditions, where the
substrate pair undergoes a tandem [2+2] cycloaddition followed by rearrangement, delivering the
Coumarin (2H-1-benzopyran-2-one) and
its derivatives exhibit a broad spectrum of
pharmacological activities, including anti-in-
flammatory, antibacterial, antiviral, antiox-
idant, antithrombotic, anti-Alzheimer, and
anticancer properties [190]. In this context,
Tan et al. (Scheme 39) [191] reported a visi-
ble-light-induced, photoredox-catalyzed tan-
dem radical addition/cyclization of 2-alkenyl-
phenols 99 with carbon tetrabromide (CBr₄)
to access a variety of 4-arylcoumarins 100 in a
one-pot fashion. The reaction proceeds under
mild, redox-neutral conditions and demon-
strates good functional-group tolerance, oper-
ational simplicity, and scalability. Preliminary
mechanistic studies confirm the radical nature
of the process and highlight the essential role
of water as an additive. The transformation
is typically conducted in CH₂Cl₂ at ambient
temperature with water (5 equiv.) and K₂CO₃
(1.5 equiv.), using fac-Ir(ppy)3 (2 mol%) as
photocatalyst and 7 W blue LEDs for irradia-
tion. The desired coumarin derivatives 100 are
isolated in yields ranging from 52% to 95%.
Importantly, fluorination in the final products
100 may be introduced on both aromatic rings,
either as monofluorinated substituents or in
combination with trifluoromethyl groups, of-
fering considerable structural diversity. This
enables the design of fluorinated coumarin
derivatives with enhanced medicinal relevance
and tunable physicochemical profiles.
Fluorinated indoles are widely recognized
as valuable end products due to their potent
bioactivity. However, they also serve as versa-
tile synthetic intermediates for accessing more
complex molecular architectures with desira-
ble biological and physicochemical properties
[192]. In this context, Wu et al. (Scheme 40)
[193] developed a visible-light-driven oxida-
tive cyclization protocol utilizing fluorinated
3-alkenylindoles 101 and styrene 102 to con-
struct carbazole derivatives 103. The trans-
formation is enabled by Ir(dtbbpy)(ppy)2PF₆
54 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
(2 mol%) under aerobic conditions, where
the substrate pair undergoes a tandem [2+2]
cycloaddition followed by rearrangement, de-
livering the targeted carbazole frameworks
in good to excellent yields (50–79%). Mecha-
nistic studies reveal that the process proceeds
through photoinduced energy transfer, sub-
sequently followed by electron transfer, estab-
lishing a dual activation pathway. Reactions
are performed in a CH₂Cl₂/DMSO solvent
system under blue LED irradiation at ambient
temperature for 12 hours.
sequence starting from trifluoroacetic acid and benzylamine, as illustrated in Scheme 38 [189].
Scheme 38. Synthesis of 2,2,2-trifluoroethylamine via [1,3]-proton shift reaction.
Coumarin (2H-1-benzopyran-2-one) and its derivatives exhibit a broad spectrum of
pharmacological activities, including anti-inflammatory, antibacterial, antiviral, antioxidant,
antithrombotic, anti-Alzheimer, and anticancer properties [190]. In this context, Tan et al. (Scheme
39) [191] reported a visible-light-induced, photoredox-catalyzed tandem radical addition/cyclization
of 2-alkenylphenols 99 with carbon tetrabromide (CBr₄) to access a variety of 4-arylcoumarins 100
in a one-pot fashion. The reaction proceeds under mild, redox-neutral conditions and demonstrates
good functional-group tolerance, operational simplicity, and scalability. Preliminary mechanistic
studies confirm the radical nature of the process and highlight the essential role of water as an
additive. The transformation is typically conducted in CH₂Cl₂ at ambient temperature with water (5
equiv.) and K₂CO₃ (1.5 equiv.), using fac-Ir(ppy)3 (2 mol%) as photocatalyst and 7 W blue LEDs for
irradiation. The desired coumarin derivatives 100 are isolated in yields ranging from 52% to 95%.
Importantly, fluorination in the final products 100 may be introduced on both aromatic rings, either
as monofluorinated substituents or in combination with trifluoromethyl groups, offering
considerable structural diversity. This enables the design of fluorinated coumarin derivatives with
enhanced medicinal relevance and tunable physicochemical profiles.
Scheme 39. Synthesis of fluorinated 4-arylcoumarins.
Fluorinated indoles are widely recognized as valuable end products due to their potent bioactivity.
However, they also serve as versatile synthetic intermediates for accessing more complex molecular
architectures with desirable biological and physicochemical properties [192]. In this context, Wu et
al. (Scheme 40) [193] developed a visible-light-driven oxidative cyclization protocol utilizing
fluorinated 3-alkenylindoles 101 and styrene 102 to construct carbazole derivatives 103. The
transformation is enabled by Ir(dtbbpy)(ppy)2PF₆ (2 mol%) under aerobic conditions, where the
substrate pair undergoes a tandem [2+2] cycloaddition followed by rearrangement, delivering the
Scheme 39. Synthesis of fluorinated 4-arylcoumarins.
Scheme 40. Synthesis of fluorinated carbazoles.
targeted carbazole frameworks in good to excellent yields (50–79%). Mechanistic studies reveal
that the process proceeds through photoinduced energy transfer, subsequently followed by electron
transfer, establishing a dual activation pathway. Reactions are performed in a CH₂Cl₂/DMSO
solvent system under blue LED irradiation at ambient temperature for 12 hours.
Scheme 40. Synthesis of fluorinated carbazoles.
Chen et al. (Scheme 41) [194] reported a visible-light-induced alkoxycarbonyl-radical-triggered
cascade cyclization of 1,7-enynes 104 using alkyloxalyl chlorides 105 as esterifying agents,
enabling the efficient synthesis of benzo[j]phenanthridine derivatives 106. The methodology
demonstrates broad compatibility with diverse alkoxycarbonyl radical precursors and achieves
selective incorporation of ester functionalities into polycyclic frameworks. This radical cascade
exhibits mild reaction conditions, excellent functional group tolerance, and yields ranging from
52% to 95%. The transformation is typically conducted in acetonitrile at 40–50 °C for 36 hours,
employing 2,6-lutidine as a base to neutralize evolving HCl. Photochemical activation is
accomplished using Ir(ppy)3 (2 mol%) under blue LED irradiation. Importantly, the protocol allows
strategic fluorine incorporation—either a single fluorine atom or a trifluoromethyl group—on both
aromatic rings adjacent to the alkyne moiety in the starting enynes 104, and correspondingly in the
final products 106. This structural flexibility enhances the method’s utility for constructing fluorine-
rich polycyclic compounds, supporting the development of tailored molecular scaffolds for
medicinal chemistry and bioactivity profiling.
Scheme 41. Synthesis of ester-substituted benzo[j]phenanthridines.
Cyclopropane α-amino acids represent a compelling class of sterically constrained amino acid
derivatives, with both naturally occurring and synthetic examples attracting sustained interest in
medicinal chemistry and drug discovery [52, 195]. Their rigid three-membered ring imparts unique
conformational properties, making them valuable scaffolds for modulating biological activity and
metabolic stability. Of particular significance are fluorinated cyclopropane α-amino acids, which are
being intensively investigated as key structural motifs in the design of highly potent inhibitors
targeting the hepatitis C virus (HCV) NS3/4A protease [196–198]. These fluorinated analogs
contribute to improved lipophilicity, binding affinity, and resistance to enzymatic degradation—
Chen et al. (Scheme 41) [194] reported a
visible-light-induced alkoxycarbonyl-radical-
triggered cascade cyclization of 1,7-enynes
104 using alkyloxalyl chlorides 105 as esteri-
fying agents, enabling the efficient synthesis of
benzo[j]phenanthridine derivatives 106. The
methodology demonstrates broad compati-
bility with diverse alkoxycarbonyl radical pre-
cursors and achieves selective incorporation
of ester functionalities into polycyclic frame-
works. This radical cascade exhibits mild reac-
tion conditions, excellent functional group tol-
erance, and yields ranging from 52% to 95%.
The transformation is typically conducted in
acetonitrile at 40–50 °C for 36 hours, employ-
ing 2,6-lutidine as a base to neutralize evolv-
ing HCl. Photochemical activation is accom-
plished using Ir(ppy)3 (2 mol%) under blue
LED irradiation. Importantly, the protocol
allows strategic fluorine incorporation—either
a single fluorine atom or a trifluoromethyl
group—on both aromatic rings adjacent to the
55https://ucj.org.ua
Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
alkyne moiety in the starting enynes 104, and
correspondingly in the final products 106. This
structural flexibility enhances the method’s
utility for constructing fluorine-rich polycyc
lic compounds, supporting the development
of tailored molecular scaffolds for medicinal
chemistry and bioactivity profiling.
targeted carbazole frameworks in good to excellent yields (50–79%). Mechanistic studies reveal
that the process proceeds through photoinduced energy transfer, subsequently followed by electron
transfer, establishing a dual activation pathway. Reactions are performed in a CH₂Cl₂/DMSO
solvent system under blue LED irradiation at ambient temperature for 12 hours.
Scheme 40. Synthesis of fluorinated carbazoles.
Chen et al. (Scheme 41) [194] reported a visible-light-induced alkoxycarbonyl-radical-triggered
cascade cyclization of 1,7-enynes 104 using alkyloxalyl chlorides 105 as esterifying agents,
enabling the efficient synthesis of benzo[j]phenanthridine derivatives 106. The methodology
demonstrates broad compatibility with diverse alkoxycarbonyl radical precursors and achieves
selective incorporation of ester functionalities into polycyclic frameworks. This radical cascade
exhibits mild reaction conditions, excellent functional group tolerance, and yields ranging from
52% to 95%. The transformation is typically conducted in acetonitrile at 40–50 °C for 36 hours,
employing 2,6-lutidine as a base to neutralize evolving HCl. Photochemical activation is
accomplished using Ir(ppy)3 (2 mol%) under blue LED irradiation. Importantly, the protocol allows
strategic fluorine incorporation—either a single fluorine atom or a trifluoromethyl group—on both
aromatic rings adjacent to the alkyne moiety in the starting enynes 104, and correspondingly in the
final products 106. This structural flexibility enhances the method’s utility for constructing fluorine-
rich polycyclic compounds, supporting the development of tailored molecular scaffolds for
medicinal chemistry and bioactivity profiling.
Scheme 41. Synthesis of ester-substituted benzo[j]phenanthridines.
Cyclopropane α-amino acids represent a compelling class of sterically constrained amino acid
derivatives, with both naturally occurring and synthetic examples attracting sustained interest in
medicinal chemistry and drug discovery [52, 195]. Their rigid three-membered ring imparts unique
conformational properties, making them valuable scaffolds for modulating biological activity and
metabolic stability. Of particular significance are fluorinated cyclopropane α-amino acids, which are
being intensively investigated as key structural motifs in the design of highly potent inhibitors
targeting the hepatitis C virus (HCV) NS3/4A protease [196–198]. These fluorinated analogs
contribute to improved lipophilicity, binding affinity, and resistance to enzymatic degradation—
Scheme 41. Synthesis of ester-substituted benzo[j]phenanthridines.
Cyclopropane α-amino acids represent a
compelling class of sterically constrained amino
acid derivatives, with both naturally occurring
and synthetic examples attracting sustained
interest in medicinal chemistry and drug dis
covery [52, 195]. Their rigid three-membered
ring imparts unique conformational properties,
making them valuable scaffolds for modulating
biological activity and metabolic stability. Of
particular significance are fluorinated cyclo-
propane α-amino acids, which are being inten-
sively investigated as key structural motifs in
the design of highly potent inhibitors targeting
the hepatitis C virus (HCV) NS3/4A protease
[196–198]. These fluorinated analogs contrib-
ute to improved lipophilicity, binding affinity,
and resistance to enzymatic degradation—fea-
tures critical to antiviral therapeutic develop-
ment. In this context, Huang et al. (Scheme 42)
[199] reported an efficient strategy for the syn-
thesis of cyclopropane-fused indolines 109 via
a photoredox-catalyzed dearomative cyclopro-
panation of indole derivatives 107 with reagent
108. The methodology accommodates a broad
array of functionalized indoles and proceeds
under mild conditions, delivering the desired
products in moderate to excellent yields. To
demonstrate the synthetic utility, reactions were
successfully scaled to 5 mmol and product deri-
vatizations were performed, highlighting the
versatility of the approach. The transformation
is conducted in DMSO at ambient temperature
using Ir[dF(CF₃)ppy]2(dtbbpy)]PF₆ (3 mol%) as
photocatalyst under 3 W blue LED irradiation
for 24 hours. The resulting cyclopropane amino
acid-fused indolines 109 are obtained in 30–
93% yields depending on substrate variation.
Importantly, fluorination is introduced through
various fluorine substituents positioned on the
aromatic rings of both the starting indoles 107
and the final products 109. This flexible fluorine
incorporation expands the structural diversity
of the indoline scaffolds and supports the con-
struction of fluorinated compound libraries for
medicinal chemistry and molecular optimiza-
tion studies.
56 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
Scheme 42. Preparation of cyclopropane fused indolines.
features critical to antiviral therapeutic development. In this context, Huang et al. (Scheme 42)
[199] reported an efficient strategy for the synthesis of cyclopropane-fused indolines 109 via a
photoredox-catalyzed dearomative cyclopropanation of indole derivatives 107 with reagent 108.
The methodology accommodates a broad array of functionalized indoles and proceeds under mild
conditions, delivering the desired products in moderate to excellent yields. To demonstrate the
synthetic utility, reactions were successfully scaled to 5 mmol and product derivatizations were
performed, highlighting the versatility of the approach. The transformation is conducted in DMSO
at ambient temperature using Ir[dF(CF₃)ppy]2(dtbbpy)]PF₆ (3 mol%) as photocatalyst under 3 W
blue LED irradiation for 24 hours. The resulting cyclopropane amino acid-fused indolines 109 are
obtained in 30–93% yields depending on substrate variation. Importantly, fluorination is introduced
through various fluorine substituents positioned on the aromatic rings of both the starting indoles
107 and the final products 109. This flexible fluorine incorporation expands the structural diversity
of the indoline scaffolds and supports the construction of fluorinated compound libraries for
medicinal chemistry and molecular optimization studies.
Scheme 42. Preparation of cyclopropane fused indolines.
Xie et al. (Scheme 43) [200] reported a visible-light-induced radical cascade reaction between 2-
alkynylarylethers 110 and sodium sulfinates 111, enabling the efficient synthesis of sulfonyl-
functionalized dihydrobenzofurans 112. The transformation proceeds via an intramolecular 1,5-
hydrogen atom transfer (1,5-HAT) mechanism, followed by C–C bond formation that constructs the
dihydrobenzofuran core in a streamlined manner. The protocol demonstrates broad substrate scope,
accommodating various substituents on both 2-alkynylarylethers 110 and sodium sulfinates 112 and
affords the target products 112 in moderate to good yields (20–78%). Reactions are performed in a
mixture of acetic acid and water under a nitrogen atmosphere for 24 hours. Photochemical
activation is achieved using Ir(ppy)2(dtbbpy)]PF₆ (2 mol%) as the catalyst, with 30 W blue LEDs
serving as the light source. Fluorination is incorporated through either mono-fluorine atoms or
trifluoromethyl groups positioned on the aromatic ring of the starting materials 110 and retained in
the final dihydrobenzofuran products 112. This versatility supports the generation of fluorinated
heterocycles with potential relevance for medicinal chemistry, structure–activity exploration, and
property tuning.
Scheme 43. Synthesis of dihydrobenzofurans.
Zhang et al. (Scheme 44) [201] reported a mild and efficient protocol for the synthesis of
substituted quinazolines 115 via visible-light-induced benzylic C–H functionalization, employing
features critical to antiviral therapeutic development. In this context, Huang et al. (Scheme 42)
[199] reported an efficient strategy for the synthesis of cyclopropane-fused indolines 109 via a
photoredox-catalyzed dearomative cyclopropanation of indole derivatives 107 with reagent 108.
The methodology accommodates a broad array of functionalized indoles and proceeds under mild
conditions, delivering the desired products in moderate to excellent yields. To demonstrate the
synthetic utility, reactions were successfully scaled to 5 mmol and product derivatizations were
performed, highlighting the versatility of the approach. The transformation is conducted in DMSO
at ambient temperature using Ir[dF(CF₃)ppy]2(dtbbpy)]PF₆ (3 mol%) as photocatalyst under 3 W
blue LED irradiation for 24 hours. The resulting cyclopropane amino acid-fused indolines 109 are
obtained in 30–93% yields depending on substrate variation. Importantly, fluorination is introduced
through various fluorine substituents positioned on the aromatic rings of both the starting indoles
107 and the final products 109. This flexible fluorine incorporation expands the structural diversity
of the indoline scaffolds and supports the construction of fluorinated compound libraries for
medicinal chemistry and molecular optimization studies.
Scheme 42. Preparation of cyclopropane fused indolines.
Xie et al. (Scheme 43) [200] reported a visible-light-induced radical cascade reaction between 2-
alkynylarylethers 110 and sodium sulfinates 111, enabling the efficient synthesis of sulfonyl-
functionalized dihydrobenzofurans 112. The transformation proceeds via an intramolecular 1,5-
hydrogen atom transfer (1,5-HAT) mechanism, followed by C–C bond formation that constructs the
dihydrobenzofuran core in a streamlined manner. The protocol demonstrates broad substrate scope,
accommodating various substituents on both 2-alkynylarylethers 110 and sodium sulfinates 112 and
affords the target products 112 in moderate to good yields (20–78%). Reactions are performed in a
mixture of acetic acid and water under a nitrogen atmosphere for 24 hours. Photochemical
activation is achieved using Ir(ppy)2(dtbbpy)]PF₆ (2 mol%) as the catalyst, with 30 W blue LEDs
serving as the light source. Fluorination is incorporated through either mono-fluorine atoms or
trifluoromethyl groups positioned on the aromatic ring of the starting materials 110 and retained in
the final dihydrobenzofuran products 112. This versatility supports the generation of fluorinated
heterocycles with potential relevance for medicinal chemistry, structure–activity exploration, and
property tuning.
Scheme 43. Synthesis of dihydrobenzofurans.
Zhang et al. (Scheme 44) [201] reported a mild and efficient protocol for the synthesis of
substituted quinazolines 115 via visible-light-induced benzylic C–H functionalization, employing
Xie et al. (Scheme 43) [200] reported a vi
sible-light-induced radical cascade reaction
between 2-alkynylarylethers 110 and sodium
sulfinates 111, enabling the efficient synthesis
of sulfonyl-functionalized dihydrobenzofu-
rans 112. The transformation proceeds via an
intramolecular 1,5-hydrogen atom transfer
(1,5-HAT) mechanism, followed by C–C bond
formation that constructs the dihydroben-
zofuran core in a streamlined manner. The
protocol demonstrates broad substrate scope,
accommodating various substituents on both
2-alkynylarylethers 110 and sodium sulfinates
112 and affords the target products 112 in mo
derate to good yields (20–78%). Reactions are
performed in a mixture of acetic acid and wa-
ter under a nitrogen atmosphere for 24 hours.
Photochemical activation is achieved using
Ir(ppy)2(dtbbpy)]PF₆ (2 mol%) as the cata-
lyst, with 30 W blue LEDs serving as the light
source. Fluorination is incorporated through
either mono-fluorine atoms or trifluoromethyl
groups positioned on the aromatic ring of the
starting materials 110 and retained in the final
dihydrobenzofuran products 112. This versa-
tility supports the generation of fluorinated
heterocycles with potential relevance for me-
dicinal chemistry, structure–activity explora-
tion, and property tuning.
Scheme 43. Synthesis of dihydrobenzofurans.
Zhang et al. (Scheme 44) [201] reported
a mild and efficient protocol for the synthe-
sis of substituted quinazolines 115 via visi-
ble-light-induced benzylic C–H functional-
ization, employing benzophenones 113 and
benzylamines 114 as starting materials. The
transformation proceeds under a nitrogen at-
mosphere at room temperature, using tert-bu-
tyl peroxybenzoate (TBPB) (4 equiv.) as the
radical initiator and Li₂CO₃ (3 equiv.) as a
base, with Ir(ppy)₃ (1 mol%) as the photocata-
lyst and blue LED irradiation for 12 hours. The
reaction exhibits high chemoselectivity and
affords the quinazoline products 115 in yields
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ranging from 45% to 85%. Fluorine incorpo-
ration is achieved using trifluoromethyl-sub-
stituted benzylamines 114, which translate
into trifluoromethylphenyl motifs in the final
quinazoline products 115, enhancing their po-
tential for medicinal chemistry applications.
It is worth noting that both starting materi-
als are readily available and synthetically ver-
satile.
Ortho-amino benzo- and acetophenones
113 are widely utilized in the synthesis of
benzodiazepines [202] and in the design of
tridentate ligands for asymmetric synthesis
of tailor-made amino acids [203–206]. Tri
fluorobenzylamines 114 have found applica-
tion in biomimetic transamination strategies,
contributing to the synthesis of fluorinated
amines and bioactive scaffolds [207–209].
Scheme 44. Synthesis of 2-arylquinazolines.
benzophenones 113 and benzylamines 114 as starting materials. The transformation proceeds under
a nitrogen atmosphere at room temperature, using tert-butyl peroxybenzoate (TBPB) (4 equiv.) as
the radical initiator and Li₂CO₃ (3 equiv.) as a base, with Ir(ppy)₃ (1 mol%) as the photocatalyst and
blue LED irradiation for 12 hours. The reaction exhibits high chemoselectivity and affords the
quinazoline products 115 in yields ranging from 45% to 85%. Fluorine incorporation is achieved
using trifluoromethyl-substituted benzylamines 114, which translate into trifluoromethylphenyl
motifs in the final quinazoline products 115, enhancing their potential for medicinal chemistry
applications.
It is worth noting that both starting materials are readily available and synthetically versatile.
Ortho-amino benzo- and acetophenones 113 are widely utilized in the synthesis of benzodiazepines
[202] and in the design of tridentate ligands for asymmetric synthesis of tailor-made amino acids
[203–206]. Trifluorobenzylamines 114 have found application in biomimetic transamination
strategies, contributing to the synthesis of fluorinated amines and bioactive scaffolds [207–209].
Scheme 44. Synthesis of 2-arylquinazolines.
Wang et al. (Scheme 45) [210] reported a visible-light-accelerated C–H annulation strategy
catalyzed by [Cp*RhCl₂]₂ (2.5 mol%), enabling the synthesis of bridged tetrahydrobenzocarbazoles
118 from aromatic amines 116 and bicyclic alkenes 117. This transformation leverages the
synergistic effect of rhodium catalysis and visible-light irradiation (40 W blue LEDs), allowing
diverse 116 substrates to react efficiently with azabicyclic alkenes 117 under ambient conditions.
The reactions are typically performed in 1,2-dichloroethane (DCE) under an argon atmosphere at
room temperature for 12 hours, affording the desired bridged oxa- or aza-tetrahydrobenzocarbazoles
118 in good to excellent yields (53–98%). Fluorination is introduced via the starting anilines 116,
which may bear either a monofluorine substituent or a trifluoromethyl group, contributing to the
structural diversity and potential pharmacological relevance of the final products 118.
Scheme 45. Synthesis of tetrahydro benzocarbazoles.
Indoles represent a cornerstone scaffold in drug design, prized for their broad-spectrum biological
activity and ability to engage diverse molecular targets. Found extensively in both natural products
and synthetic pharmaceuticals, indole-based compounds play pivotal roles in anticancer,
benzophenones 113 and benzylamines 114 as starting materials. The transformation proceeds under
a nitrogen atmosphere at room temperature, using tert-butyl peroxybenzoate (TBPB) (4 equiv.) as
the radical initiator and Li₂CO₃ (3 equiv.) as a base, with Ir(ppy)₃ (1 mol%) as the photocatalyst and
blue LED irradiation for 12 hours. The reaction exhibits high chemoselectivity and affords the
quinazoline products 115 in yields ranging from 45% to 85%. Fluorine incorporation is achieved
using trifluoromethyl-substituted benzylamines 114, which translate into trifluoromethylphenyl
motifs in the final quinazoline products 115, enhancing their potential for medicinal chemistry
applications.
It is worth noting that both starting materials are readily available and synthetically versatile.
Ortho-amino benzo- and acetophenones 113 are widely utilized in the synthesis of benzodiazepines
[202] and in the design of tridentate ligands for asymmetric synthesis of tailor-made amino acids
[203–206]. Trifluorobenzylamines 114 have found application in biomimetic transamination
strategies, contributing to the synthesis of fluorinated amines and bioactive scaffolds [207–209].
Scheme 44. Synthesis of 2-arylquinazolines.
Wang et al. (Scheme 45) [210] reported a visible-light-accelerated C–H annulation strategy
catalyzed by [Cp*RhCl₂]₂ (2.5 mol%), enabling the synthesis of bridged tetrahydrobenzocarbazoles
118 from aromatic amines 116 and bicyclic alkenes 117. This transformation leverages the
synergistic effect of rhodium catalysis and visible-light irradiation (40 W blue LEDs), allowing
diverse 116 substrates to react efficiently with azabicyclic alkenes 117 under ambient conditions.
The reactions are typically performed in 1,2-dichloroethane (DCE) under an argon atmosphere at
room temperature for 12 hours, affording the desired bridged oxa- or aza-tetrahydrobenzocarbazoles
118 in good to excellent yields (53–98%). Fluorination is introduced via the starting anilines 116,
which may bear either a monofluorine substituent or a trifluoromethyl group, contributing to the
structural diversity and potential pharmacological relevance of the final products 118.
Scheme 45. Synthesis of tetrahydro benzocarbazoles.
Indoles represent a cornerstone scaffold in drug design, prized for their broad-spectrum biological
activity and ability to engage diverse molecular targets. Found extensively in both natural products
and synthetic pharmaceuticals, indole-based compounds play pivotal roles in anticancer,
Wang et al. (Scheme 45) [210] reported a
visible-light-accelerated C–H annulation strat-
egy catalyzed by [Cp*RhCl₂]₂ (2.5 mol%), en-
abling the synthesis of bridged tetrahydroben-
zocarbazoles 118 from aromatic amines 116
and bicyclic alkenes 117. This transformation
leverages the synergistic effect of rhodium ca-
talysis and visible-light irradiation (40 W blue
LEDs), allowing diverse 116 substrates to react
efficiently with azabicyclic alkenes 117 under
ambient conditions. The reactions are typically
performed in 1,2-dichloroethane (DCE) under
an argon atmosphere at room temperature for
12 hours, affording the desired bridged oxa- or
aza-tetrahydrobenzocarbazoles 118 in good to
excellent yields (53–98%). Fluorination is in-
troduced via the starting anilines 116, which
may bear either a monofluorine substituent or
a trifluoromethyl group, contributing to the
structural diversity and potential pharmaco-
logical relevance of the final products 118.
Scheme 45. Synthesis of tetrahydro benzocarbazoles.
58 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
Indoles represent a cornerstone scaffold in
drug design, prized for their broad-spectrum
biological activity and ability to engage diverse
molecular targets. Found extensively in both
natural products and synthetic pharmaceu-
ticals, indole-based compounds play pivotal
roles in anticancer, antimicrobial, anti-inflam-
matory, and neuroprotective therapies. Their
structural flexibility allows medicinal chemists
to fine-tune potency, selectivity, and bioavai
lability, making indoles indispensable in con-
temporary drug discovery efforts [211–214].
A wide array of synthetic strategies has
been developed for the construction of indole
derivatives [215–218], including those bearing
fluorine substituents, which enhance meta-
bolic stability and target specificity [219–222].
In this work, we have already discussed se
veral methodologies for the preparation of in-
dole-based compounds. The following sections
will further expand on the application of in-
doles and their derivatives as both starting ma-
terials and products in a variety of innovative
photochemical transformations, highlighting
their continued relevance in synthetic and me-
dicinal chemistry.
Fluorine-containing tryptophans are bio-
logically significant compounds with intrin-
sic pharmacological relevance [223–225].
Their use as starting materials is particularly
attractive, as they enable the construction of
indole-based scaffolds bearing pharmacopho
ric units, thereby expanding the chemical
space for drug discovery. In this context, Li
et al. (Scheme 46) [226] reported a facile and
efficient synthesis of multi-substituted trans-
fused hexahydrocarbazoles 121 via a stereose-
lective intermolecular radical cascade reaction
between readily available substituted trypto-
phans 119 (including fluorinated variants) and
acrylamides 120. The transformation is ena-
bled by visible-light-induced photoredox ca-
talysis, delivering the target products in up to
82% yield with >20:1 diastereoselectivity, and
forming four stereocenters, including two qua-
ternary centers. Interestingly, when the reac-
tion is conducted under ambient air, the major
products shift toward tetrahydrocarbazoles,
suggesting oxygen influences the radical path-
way. Preliminary mechanistic studies indicate
a sequence involving radical addition cascades
followed by radical–polar crossover events.
The reactions are performed in DMA at 30 °C
under an argon atmosphere, using Na₂CO₃
(3 equiv.) as a base. Photochemical activation
is achieved with Ir[dF(CF₃)ppy]₂(dtbbpy)]PF₆
(1 mol%) under blue LED irradiation. Fluo
rination is introduced through multiple vec-
tors: the trifluoromethyl group on the starting
2-(trifluoromethyl)acrylamides 120 and fluo-
rine atoms on the aromatic rings of both 119
and 120, resulting in multi-fluorinated hexa
hydrocarbazole products 121 with enhanced
structural and physicochemical diversity.
antimicrobial, anti-inflammatory, and neuroprotective therapies. Their structural flexibility allows
medicinal chemists to fine-tune potency, selectivity, and bioavailability, making indoles
indispensable in contemporary drug discovery efforts [211–214].
A wide array of synthetic strategies has been developed for the construction of indole derivatives
[215–218], including those bearing fluorine substituents, which enhance metabolic stability and
target specificity [219–222]. In this work, we have already discussed several methodologies for the
preparation of indole-based compounds. The following sections will further expand on the
application of indoles and their derivatives as both starting materials and products in a variety of
innovative photochemical transformations, highlighting their continued relevance in synthetic and
medicinal chemistry.
Fluorine-containing tryptophans are biologically significant compounds with intrinsic
pharmacological relevance [223–225]. Their use as starting materials is particularly attractive, as
they enable the construction of indole-based scaffolds bearing pharmacophoric units, thereby
expanding the chemical space for drug discovery. In this context, Li et al. (Scheme 46) [226]
reported a facile and efficient synthesis of multi-substituted trans-fused hexahydrocarbazoles 121
via a stereoselective intermolecular radical cascade reaction between readily available substituted
tryptophans 119 (including fluorinated variants) and acrylamides 120. The transformation is enabled
by visible-light-induced photoredox catalysis, delivering the target products in up to 82% yield with
>20:1 diastereoselectivity, and forming four stereocenters, including two quaternary centers.
Interestingly, when the reaction is conducted under ambient air, the major products shift toward
tetrahydrocarbazoles, suggesting oxygen influences the radical pathway. Preliminary mechanistic
studies indicate a sequence involving radical addition cascades followed by radical–polar crossover
events. The reactions are performed in DMA at 30 °C under an argon atmosphere, using Na₂CO₃ (3
equiv.) as a base. Photochemical activation is achieved with Ir[dF(CF₃)ppy]₂(dtbbpy)]PF₆ (1 mol%)
under blue LED irradiation. Fluorination is introduced through multiple vectors: the trifluoromethyl
group on the starting 2-(trifluoromethyl)acrylamides 120 and fluorine atoms on the aromatic rings
of both 119 and 120, resulting in multi-fluorinated hexahydrocarbazole products 121 with enhanced
structural and physicochemical diversity.
Scheme 46. Synthesis of fluorinated hexahydrocarbazoles.
The stereochemical outcome of these reactions warrants particular emphasis. The simultaneous
formation of four stereogenic centers with exceptional diastereoselectivity (>20:1) is a remarkable
achievement, underscoring the stereocontrolling influence of the trifluoromethyl group [227, 228].
Such high-level stereochemical precision is rarely observed in radical cascade processes and
highlights the strategic value of fluorinated motifs in stereoselective synthesis. Moreover, the 2-
(trifluoromethyl)acrylamides 120 employed in these transformations are exceptionally reactive
Michael acceptors, owing to the strong electron-withdrawing nature of the CF₃ group. Their
reactivity has been successfully harnessed in the synthesis of trifluoromethylated derivatives of
glutamic acid and related analogs, expanding their utility in the construction of fluorine-rich
Scheme 46. Synthesis of fluorinated hexahydrocarbazoles.
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The stereochemical outcome of these reac-
tions warrants particular emphasis. The simul-
taneous formation of four stereogenic centers
with exceptional diastereoselectivity (>20:1) is
a remarkable achievement, underscoring the
stereocontrolling influence of the trifluorome-
thyl group [227, 228]. Such high-level stereo-
chemical precision is rarely observed in radical
cascade processes and highlights the strategic
value of fluorinated motifs in stereoselective
synthesis. Moreover, the 2-(trifluoromethyl)
acrylamides 120 employed in these transfor-
mations are exceptionally reactive Michael
acceptors, owing to the strong electron-with-
drawing nature of the CF₃ group. Their reac-
tivity has been successfully harnessed in the
synthesis of trifluoromethylated derivatives of
glutamic acid and related analogs, expanding
their utility in the construction of fluorine-rich
bioactive frameworks [229–231].
Kim et al. (Scheme 47) [232] reported a
direct C–H functionalization/cyclization of
acetanilides 122 with alkyne derivatives 123,
enabled by a dual catalytic system involving
photoredox and transition-metal catalysis. The
reaction employed a readily available photore-
dox catalyst, [Ru(dtbbpy)₂(bpy)]PF₆ (1 mol%),
in combination with [RhCp*Cl₂]₂ (2 mol%),
a well-established catalyst for C–H activa-
tion. Under irradiation with an 11 W compact
fluorescent lamp (CFL), the transformation
proceeded smoothly to furnish indoles 124
in good yields (33–88%). Mechanistic inves-
tigations revealed that each catalyst operates
independently, contributing distinct roles to
the overall transformation. The reactions were
carried out in chlorobenzene at 120 °C for
12 hours, with AgSbF₆ (8 mol%) as an addi-
tive to facilitate catalyst activation. Fluorinated
motifs were incorporated both as fluorine at-
oms and trifluoromethyl groups on the start-
ing anilines 122, and these substituents were
retained on the benzene ring of the resulting
indoles 124, highlighting the method’s com-
patibility with fluorinated substrates.
Scheme 47. Synthesis of fluorinated indoles.
bioactive frameworks [229–231].
Kim et al. (Scheme 47) [232] reported a direct C–H functionalization/cyclization of acetanilides
122 with alkyne derivatives 123, enabled by a dual catalytic system involving photoredox and
transition-metal catalysis. The reaction employed a readily available photoredox catalyst,
[Ru(dtbbpy)₂(bpy)]PF₆ (1 mol%), in combination with [RhCp*Cl₂]₂ (2 mol%), a well-established
catalyst for C–H activation. Under irradiation with an 11 W compact fluorescent lamp (CFL), the
transformation proceeded smoothly to furnish indoles 124 in good yields (33–88%). Mechanistic
investigations revealed that each catalyst operates independently, contributing distinct roles to the
overall transformation. The reactions were carried out in chlorobenzene at 120 °C for 12 hours, with
AgSbF₆ (8 mol%) as an additive to facilitate catalyst activation. Fluorinated motifs were
incorporated both as fluorine atoms and trifluoromethyl groups on the starting anilines 122, and
these substituents were retained on the benzene ring of the resulting indoles 124, highlighting the
method’s compatibility with fluorinated substrates.
Scheme 47. Synthesis of fluorinated indoles.
Lin et al. (Scheme 48) [233] reported a mild and efficient protocol for the visible-light-induced
radical cascade difluoromethylation/cyclization of indoles bearing unactivated alkenes 125. The
transformation utilizes a bench-stable and readily accessible difluoromethyltriphenylphosphonium
bromide 126 as a precursor for the –CF₂H group, enabling the synthesis of CF₂H-substituted
polycyclic indole derivatives 127 in moderate to good yields (50–90%). This strategy is notable for
its ability to construct C(sp³)–CF₂H and C–C bonds under additive-free conditions, with simple
operational setup, ambient temperature, and a broad substrate scope. Mechanistic investigations
confirm the involvement of a difluoromethyl radical pathway as central to the transformation.
Reactions are performed in acetonitrile at room temperature for 16 hours, using fac-Ir(ppy)₃ (2
mol%) as the photocatalyst under 5 W blue LED irradiation. Fluorine substituents are incorporated
both on the aromatic rings of the starting indoles 125 and retained in the final polycyclic products
127, contributing to the structural and physicochemical diversity of the resulting compounds.
Scheme 48. Preparation of difluoromethyl-containing indoles.
Owing to the strong electron-withdrawing effect of fluorine, fluorinated benzaldehydes exhibit high
reactivity, particularly in asymmetric aldol addition reactions [234–236]. Leveraging this reactivity,
Lin et al. (Scheme 48) [233] reported a mild
and efficient protocol for the visible-light-in-
duced radical cascade difluoromethylation/cyc
lization of indoles bearing unactivated alkenes
125. The transformation utilizes a bench-stable
and readily accessible difluoromethyltriphe-
nylphosphonium bromide 126 as a precursor
for the –CF₂H group, enabling the synthesis
of CF₂H-substituted polycyclic indole deriva-
tives 127 in moderate to good yields (50–90%).
This strategy is notable for its ability to con-
struct C(sp³)–CF₂H and C–C bonds under
additive-free conditions, with simple opera-
tional setup, ambient temperature, and a broad
60 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
substrate scope. Mechanistic investigations
confirm the involvement of a difluoromethyl
radical pathway as central to the transformation.
Reactions are performed in acetonitrile at room
temperature for 16 hours, using fac-Ir(ppy)₃
(2 mol%) as the photocatalyst under 5 W blue
LED irradiation. Fluorine substituents are in-
corporated both on the aromatic rings of the
starting indoles 125 and retained in the final
polycyclic products 127, contributing to the
structural and physicochemical diversity of the
resulting compounds.
bioactive frameworks [229–231].
Kim et al. (Scheme 47) [232] reported a direct C–H functionalization/cyclization of acetanilides
122 with alkyne derivatives 123, enabled by a dual catalytic system involving photoredox and
transition-metal catalysis. The reaction employed a readily available photoredox catalyst,
[Ru(dtbbpy)₂(bpy)]PF₆ (1 mol%), in combination with [RhCp*Cl₂]₂ (2 mol%), a well-established
catalyst for C–H activation. Under irradiation with an 11 W compact fluorescent lamp (CFL), the
transformation proceeded smoothly to furnish indoles 124 in good yields (33–88%). Mechanistic
investigations revealed that each catalyst operates independently, contributing distinct roles to the
overall transformation. The reactions were carried out in chlorobenzene at 120 °C for 12 hours, with
AgSbF₆ (8 mol%) as an additive to facilitate catalyst activation. Fluorinated motifs were
incorporated both as fluorine atoms and trifluoromethyl groups on the starting anilines 122, and
these substituents were retained on the benzene ring of the resulting indoles 124, highlighting the
method’s compatibility with fluorinated substrates.
Scheme 47. Synthesis of fluorinated indoles.
Lin et al. (Scheme 48) [233] reported a mild and efficient protocol for the visible-light-induced
radical cascade difluoromethylation/cyclization of indoles bearing unactivated alkenes 125. The
transformation utilizes a bench-stable and readily accessible difluoromethyltriphenylphosphonium
bromide 126 as a precursor for the –CF₂H group, enabling the synthesis of CF₂H-substituted
polycyclic indole derivatives 127 in moderate to good yields (50–90%). This strategy is notable for
its ability to construct C(sp³)–CF₂H and C–C bonds under additive-free conditions, with simple
operational setup, ambient temperature, and a broad substrate scope. Mechanistic investigations
confirm the involvement of a difluoromethyl radical pathway as central to the transformation.
Reactions are performed in acetonitrile at room temperature for 16 hours, using fac-Ir(ppy)₃ (2
mol%) as the photocatalyst under 5 W blue LED irradiation. Fluorine substituents are incorporated
both on the aromatic rings of the starting indoles 125 and retained in the final polycyclic products
127, contributing to the structural and physicochemical diversity of the resulting compounds.
Scheme 48. Preparation of difluoromethyl-containing indoles.
Owing to the strong electron-withdrawing effect of fluorine, fluorinated benzaldehydes exhibit high
reactivity, particularly in asymmetric aldol addition reactions [234–236]. Leveraging this reactivity,
Scheme 48. Preparation of difluoromethyl-containing indoles.
Owing to the strong electron-withdrawing
effect of fluorine, fluorinated benzaldehydes
exhibit high reactivity, particularly in asym-
metric aldol addition reactions [234–236].
Leveraging this reactivity, Liu et al. (Scheme
49) [237] developed a visible-light-induced
dual acylation strategy involving fluorobenzal-
dehydes tethered to alkenes 128 for the synthe-
sis of 3-substituted chroman-4-ones 130. The
transformation proceeds via a radical tandem
cyclization, initiated by carbon–carbon bond
cleavage of oxime esters 129 through a nitro-
gen-centered radical pathway. This method en-
ables the efficient construction of chroman-4-
one frameworks, delivering a series of 3-substi-
tuted chroman-4-ones 130 in yields up to 86%.
Reactions are typically conducted in acetone at
80 °C for 24 hours, using 2,6-lutidine (1 equiv.)
as a base. Photochemical activation is achieved
with Ir(ppy)₃ as the photocatalyst under 5 W
blue LED irradiation. Fluorine substituents,
either as single fluorine atoms or trifluorome-
thyl groups, are incorporated on the aromatic
rings of the final chromanone products 130,
contributing to their electronic diversity and
potential bioactivity.
Scheme 49. Synthesis of 3-substituted chroman-4-ones.
Liu et al. (Scheme 49) [237] developed a visible-light-induced dual acylation strategy involving
fluorobenzaldehydes tethered to alkenes 128 for the synthesis of 3-substituted chroman-4-ones 130.
The transformation proceeds via a radical tandem cyclization, initiated by carbon–carbon bond
cleavage of oxime esters 129 through a nitrogen-centered radical pathway. This method enables the
efficient construction of chroman-4-one frameworks, delivering a series of 3-substituted
chroman-4-ones 130 in yields up to 86%. Reactions are typically conducted in acetone at 80 °C for
24 hours, using 2,6-lutidine (1 equiv.) as a base. Photochemical activation is achieved with Ir(ppy)₃
as the photocatalyst under 5 W blue LED irradiation. Fluorine substituents, either as single fluorine
atoms or trifluoromethyl groups, are incorporated on the aromatic rings of the final chromanone
products 130, contributing to their electronic diversity and potential bioactivity.
Scheme 49. Synthesis of 3-substituted chroman-4-ones.
Fluorinated imines are versatile intermediates in organic synthesis, widely employed as precursors
for the construction of fluorine-containing amines and amino acids [238–240]. In this context, the
photochemical protocol reported by Li and Zhou (Scheme 50) [241] presents a mechanistically
intriguing transformation, wherein the fluorine pattern of the starting imine differs from that of the
final product. Specifically, the reaction involves the loss of one fluorine atom and a conversion from
aliphatic to aromatic fluorination, representing a rare synthetic event. The methodology utilizes
vinyldiazo reagents 132 as radical acceptors in a visible-light-promoted sequential radical
cyclization, enabling a [3+3] cyclization pathway that is mechanistically distinct from conventional
annulation strategies. Starting from N-aryl chlorodifluoromethyl alkynyl ketoimines 131, the
reaction facilitates the construction of acridine frameworks 133, incorporating a fluorine atom into
the acridine core during the simultaneous formation of both pyridine and benzene rings from acyclic
precursors. The resulting 4-fluoroacridines 133 exhibit pronounced solid-state fluorescence,
underscoring their potential utility in materials science and photonic applications. Reactions are
typically conducted in dichloromethane (DCM) at ambient temperature for 18 hours, using Hünig’s
base (3 equiv.) to scavenge acidic byproducts. Photochemical activation is achieved with
Ru(bpy)₃Cl₂ (1 mol%) under 5 W blue LED irradiation, affording mono-fluorinated acridines in
yields ranging from 37% to 79%.
Scheme 50. Synthesis of 4-fluoroacridines.
Xue et al. (Scheme 51) [242] reported a sustainable and efficient protocol for the synthesis of O-
heterocycle spiro-fused cyclopentaquinolinone derivatives 136 via a visible-light-driven radical
cascade reaction between N-(o-ethynylaryl)acrylamides 134 and O-heterocycles 135. Mechanistic
61https://ucj.org.ua
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Fluorinated imines are versatile interme
diates in organic synthesis, widely employed
as precursors for the construction of fluorine-
containing amines and amino acids [238–240].
In this context, the photochemical protocol
reported by Li and Zhou (Scheme 50) [241]
presents a mechanistically intriguing trans-
formation, wherein the fluorine pattern of
the starting imine differs from that of the fi-
nal product. Specifically, the reaction involves
the loss of one fluorine atom and a conversion
from aliphatic to aromatic fluorination, repre-
senting a rare synthetic event. The methodol-
ogy utilizes vinyldiazo reagents 132 as radical
acceptors in a visible-light-promoted sequen-
tial radical cyclization, enabling a [3+3] cy-
clization pathway that is mechanistically dis-
tinct from conventional annulation strategies.
Starting from N-aryl chlorodifluoromethyl
alkynyl ketoimines 131, the reaction facilitates
the construction of acridine frameworks 133,
incorporating a fluorine atom into the acri-
dine core during the simultaneous formation
of both pyridine and benzene rings from acy-
clic precursors. The resulting 4-fluoroacridines
133 exhibit pronounced solid-state fluores-
cence, underscoring their potential utility in
materials science and photonic applications.
Reactions are typically conducted in dichlo-
romethane (DCM) at ambient temperature for
18 hours, using Hünig’s base (3 equiv.) to scav-
enge acidic byproducts. Photochemical acti-
vation is achieved with Ru(bpy)₃Cl₂ (1 mol%)
under 5 W blue LED irradiation, affording
mono-fluorinated acridines in yields ranging
from 37% to 79%.
Liu et al. (Scheme 49) [237] developed a visible-light-induced dual acylation strategy involving
fluorobenzaldehydes tethered to alkenes 128 for the synthesis of 3-substituted chroman-4-ones 130.
The transformation proceeds via a radical tandem cyclization, initiated by carbon–carbon bond
cleavage of oxime esters 129 through a nitrogen-centered radical pathway. This method enables the
efficient construction of chroman-4-one frameworks, delivering a series of 3-substituted
chroman-4-ones 130 in yields up to 86%. Reactions are typically conducted in acetone at 80 °C for
24 hours, using 2,6-lutidine (1 equiv.) as a base. Photochemical activation is achieved with Ir(ppy)₃
as the photocatalyst under 5 W blue LED irradiation. Fluorine substituents, either as single fluorine
atoms or trifluoromethyl groups, are incorporated on the aromatic rings of the final chromanone
products 130, contributing to their electronic diversity and potential bioactivity.
Scheme 49. Synthesis of 3-substituted chroman-4-ones.
Fluorinated imines are versatile intermediates in organic synthesis, widely employed as precursors
for the construction of fluorine-containing amines and amino acids [238–240]. In this context, the
photochemical protocol reported by Li and Zhou (Scheme 50) [241] presents a mechanistically
intriguing transformation, wherein the fluorine pattern of the starting imine differs from that of the
final product. Specifically, the reaction involves the loss of one fluorine atom and a conversion from
aliphatic to aromatic fluorination, representing a rare synthetic event. The methodology utilizes
vinyldiazo reagents 132 as radical acceptors in a visible-light-promoted sequential radical
cyclization, enabling a [3+3] cyclization pathway that is mechanistically distinct from conventional
annulation strategies. Starting from N-aryl chlorodifluoromethyl alkynyl ketoimines 131, the
reaction facilitates the construction of acridine frameworks 133, incorporating a fluorine atom into
the acridine core during the simultaneous formation of both pyridine and benzene rings from acyclic
precursors. The resulting 4-fluoroacridines 133 exhibit pronounced solid-state fluorescence,
underscoring their potential utility in materials science and photonic applications. Reactions are
typically conducted in dichloromethane (DCM) at ambient temperature for 18 hours, using Hünig’s
base (3 equiv.) to scavenge acidic byproducts. Photochemical activation is achieved with
Ru(bpy)₃Cl₂ (1 mol%) under 5 W blue LED irradiation, affording mono-fluorinated acridines in
yields ranging from 37% to 79%.
Scheme 50. Synthesis of 4-fluoroacridines.
Xue et al. (Scheme 51) [242] reported a sustainable and efficient protocol for the synthesis of O-
heterocycle spiro-fused cyclopentaquinolinone derivatives 136 via a visible-light-driven radical
cascade reaction between N-(o-ethynylaryl)acrylamides 134 and O-heterocycles 135. Mechanistic
Scheme 50. Synthesis of 4-fluoroacridines.
Xue et al. (Scheme 51) [242] reported a sus-
tainable and efficient protocol for the synthesis
of O-heterocycle spiro-fused cyclopentaquino-
linone derivatives 136 via a visible-light-driven
radical cascade reaction between N-(o-ethynyl
aryl)acrylamides 134 and O-heterocycles 135.
Mechanistic studies revealed that the trans-
formation is initiated by visible-light-induced
radical generation from the O-heterocycle, fol-
lowed by regioselective radical addition onto
the acrylamide moiety. This triggers a cascade
involving 6-exo-dig and 5-endo-trig radical an-
nulations, which are terminated by single-elec-
tron oxidation and proton elimination to fur-
nish the spirocyclic products. The protocol
features broad substrate scope, extremely mild
reaction conditions, excellent atom economy,
high efficiency, and good compatibility with
diverse functional groups. Reactions are per-
formed under an argon atmosphere using TBPB
(2 equiv.) as a radical initiator, fac-Ir(ppy)₃
as the photocatalyst, and 8 W blue LED irra-
diation for 18 hours. The desired spiro-fused
cyclopentaquinolinones 136 are obtained in
yields of up to 96%. Fluorination is introduced
via mono-fluorine substitution on the aroma
tic ring of the starting acrylamides 134 and is
retained in the final products 136, contributing
to their electronic and structural diversity.
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RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
Scheme 51. Synthesis of O-heterocycle spiro-fused cyclopentaquinolinones.
studies revealed that the transformation is initiated by visible-light-induced radical generation from
the O-heterocycle, followed by regioselective radical addition onto the acrylamide moiety. This
triggers a cascade involving 6-exo-dig and 5-endo-trig radical annulations, which are terminated by
single-electron oxidation and proton elimination to furnish the spirocyclic products. The protocol
features broad substrate scope, extremely mild reaction conditions, excellent atom economy, high
efficiency, and good compatibility with diverse functional groups. Reactions are performed under
an argon atmosphere using TBPB (2 equiv.) as a radical initiator, fac-Ir(ppy)₃ as the photocatalyst,
and 8 W blue LED irradiation for 18 hours. The desired spiro-fused cyclopentaquinolinones 136 are
obtained in yields of up to 96%. Fluorination is introduced via mono-fluorine substitution on the
aromatic ring of the starting acrylamides 134 and is retained in the final products 136, contributing
to their electronic and structural diversity.
Scheme 51. Synthesis of O-heterocycle spiro-fused cyclopentaquinolinones.
Trimolecular reactions.
Trimolecular photochemical reactions are extremely rare. A true trimolecular reaction involves the
simultaneous collision of three reactant species in a single elementary step. In the context of
photochemistry, this would require three molecules to interact under light activation to form
products directly, without intermediates. The rarity of such processes arises from several
fundamental constraints. One major limitation is the low probability of three-body collisions. The
likelihood of three molecules colliding simultaneously, with the correct orientation and sufficient
energy, is less than 0.1% compared to bimolecular collisions. This statistical improbability makes
trimolecular elementary steps kinetically unfavorable under typical reaction conditions. Another
critical factor is the distribution of energy and momentum during such collisions. Even if three
molecules do collide, the energy must be partitioned in a way that allows bond formation without
immediate dissociation. Often, a third molecule is required to absorb excess energy, but this
typically occurs in stepwise mechanisms rather than true trimolecular elementary reactions.
Mechanistic complexity further limits the feasibility of trimolecular photochemical reactions. Most
reactions that appear trimolecular are actually pseudo-trimolecular, proceeding through the
formation of a binary intermediate that subsequently reacts with a third species. In photochemistry,
excited states typically undergo unimolecular or bimolecular transformations. The involvement of
three species in a concerted photochemical event is both kinetically and spectroscopically difficult
to observe or validate. Additionally, the radical nature of many photochemical reactions introduces
further challenges. Radicals are highly reactive and can follow multiple competing pathways,
making it difficult to orchestrate a trimolecular process that proceeds selectively through a single
route. As a result, successful examples of trimolecular photochemical reactions are exceedingly rare
and represent significant theoretical and practical interest in reaction design and mechanistic
exploration [243,244].
Trimolecular reactions.
Trimolecular photochemical reactions are
extremely rare. A true trimolecular reaction
involves the simultaneous collision of three
reactant species in a single elementary step.
In the context of photochemistry, this would
require three molecules to interact under light
activation to form products directly, without
intermediates. The rarity of such processes
arises from several fundamental constraints.
One major limitation is the low probability of
three-body collisions. The likelihood of three
molecules colliding simultaneously, with the
correct orientation and sufficient energy, is less
than 0.1% compared to bimolecular collisions.
This statistical improbability makes trimolec-
ular elementary steps kinetically unfavorable
under typical reaction conditions. Another
critical factor is the distribution of energy and
momentum during such collisions. Even if
three molecules do collide, the energy must be
partitioned in a way that allows bond formation
without immediate dissociation. Often, a third
molecule is required to absorb excess energy,
but this typically occurs in stepwise mecha-
nisms rather than true trimolecular elementa-
ry reactions. Mechanistic complexity further
limits the feasibility of trimolecular photo-
chemical reactions. Most reactions that appear
trimolecular are actually pseudo-trimolecular,
proceeding through the formation of a binary
intermediate that subsequently reacts with a
third species. In photochemistry, excited states
typically undergo unimolecular or bimolecu-
lar transformations. The involvement of three
species in a concerted photochemical event is
both kinetically and spectroscopically difficult
to observe or validate. Additionally, the radical
nature of many photochemical reactions intro-
duces further challenges. Radicals are highly
reactive and can follow multiple competing
pathways, making it difficult to orchestrate a
trimolecular process that proceeds selectively
through a single route. As a result, success-
ful examples of trimolecular photochemical
reactions are exceedingly rare and represent
significant theoretical and practical interest in
reaction design and mechanistic exploration
[243,244].
Liang et al. (Scheme 52) [245] reported a
visible-light-driven strategy for the synthesis
of valuable perfluoroalkylated dihydrobenzox-
azines 140 via a perfluoroalkyl radical-medi-
ated cascade reaction. The transformation in-
volves the reaction of N-tosyl-2-vinylanilines
137, Umemoto’s reagents 138, and aldehydes
139 under photoredox conditions. The reac-
tions are carried out in dichloromethane (CH₂-
Cl₂) at 5 °C in the presence of sodium acetate
(NaOAc) as a base additive. Photochemical ac-
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Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
tivation is achieved using Ir(ppy)₂(dtbbpy)PF₆
(2 mol%) as the photocatalyst under 3 W blue
LED irradiation for 4 hours. The method af-
fords perfluoroalkylated dihydrobenzoxazines
140 in good to excellent yields, ranging from
54% to 80%. Notably, the transformation is
enabled by the radical reactivity of Umemo-
to’s reagents 138, which serve as perfluoroalkyl
group donors. Fluorination is further repre-
sented by mono-fluorine and trifluoromethyl
substituents on the aromatic rings of the start-
ing N-tosyl-2-vinylanilines 137. These fluorine
motifs are retained in the final products 140,
allowing for structural diversity with one to
three fluorine atoms per molecule. This mod-
ular approach enables the synthesis of fluori-
nated heterocycles with potential applications
in agrochemicals and pharmaceuticals, owing
to the physicochemical properties imparted by
the perfluoroalkyl groups.
Scheme 52. Synthesis of fluorinated dihydrobenzoxazines.
Liang et al. (Scheme 52) [245] reported a visible-light-driven strategy for the synthesis of valuable
perfluoroalkylated dihydrobenzoxazines 140 via a perfluoroalkyl radical-mediated cascade reaction.
The transformation involves the reaction of N-tosyl-2-vinylanilines 137, Umemoto’s reagents 138,
and aldehydes 139 under photoredox conditions. The reactions are carried out in dichloromethane
(CH₂Cl₂) at 5 °C in the presence of sodium acetate (NaOAc) as a base additive. Photochemical
activation is achieved using Ir(ppy)₂(dtbbpy)PF₆ (2 mol%) as the photocatalyst under 3 W blue LED
irradiation for 4 hours. The method affords perfluoroalkylated dihydrobenzoxazines 140 in good to
excellent yields, ranging from 54% to 80%. Notably, the transformation is enabled by the radical
reactivity of Umemoto’s reagents 138, which serve as perfluoroalkyl group donors. Fluorination is
further represented by mono-fluorine and trifluoromethyl substituents on the aromatic rings of the
starting N-tosyl-2-vinylanilines 137. These fluorine motifs are retained in the final products 140,
allowing for structural diversity with one to three fluorine atoms per molecule. This modular
approach enables the synthesis of fluorinated heterocycles with potential applications in
agrochemicals and pharmaceuticals, owing to the physicochemical properties imparted by the
perfluoroalkyl groups.
Scheme 52. Synthesis of fluorinated dihydrobenzoxazines.
However, it is crucial to recognize that while certain perfluorinated compounds have found valuable
applications in life sciences and materials chemistry, a significant subset—collectively known as
per- and polyfluoroalkyl substances (PFAS)—pose substantial environmental and public health
risks. These “forever chemicals” are characterized by extreme persistence, bioaccumulative
behavior, and mobility in ecosystems, leading to widespread contamination of soil, water, and biota.
Their resistance to degradation and tendency to biomagnify through food webs have prompted
increasing regulatory scrutiny and calls for safer alternatives [147–149].
Geng et al. (Scheme 53) [246] developed a visible-light-driven three-component cyclization that
enables the direct synthesis of pyrimido[1,2-b]indazole derivatives 144 through the in situ trapping
of a 1,3-vinylimine ion intermediate. The reaction proceeds under mild conditions from
bromodifluoroacetic acid derivatives 141, enaminones 142, and 3-aminoindazoles 143. Notably, this
robust methodology allows for the efficient incorporation of aliphatic substituents and demonstrates
excellent compatibility with structurally complex bioactive molecules. This transformation
represents the first example of a photoinduced multicomponent reaction employing
bromodifluoroacetic acid derivatives as a C1 synthon. The reactions were carried out in DMSO at
room temperature using fac-Ir(ppy)₃ (2 mol%) as the photocatalyst under blue LED irradiation for
five hours. The desired pyrimido[1,2-b]indazole products 144 were obtained in moderate to good
yields, ranging from 40% to 79%. Despite their initial fluorinated structure, both fluorine atoms
from the bromodifluoroacetic acid derivatives 141 are lost during the course of the reaction.
Nevertheless, fluorination is retained through aromatic substitution on the 3-aminoindazole starting
materials 143, which is preserved in the final heterocyclic products 144. The resulting
However, it is crucial to recognize that
while certain perfluorinated compounds have
found valuable applications in life sciences and
materials chemistry, a significant subset—col-
lectively known as per- and polyfluoroalkyl
substances (PFAS)—pose substantial environ-
mental and public health risks. These “forever
chemicals” are characterized by extreme per-
sistence, bioaccumulative behavior, and mo-
bility in ecosystems, leading to widespread
contamination of soil, water, and biota. Their
resistance to degradation and tendency to bio-
magnify through food webs have prompted in-
creasing regulatory scrutiny and calls for safer
alternatives [147–149].
Geng et al. (Scheme 53) [246] developed a
visible-light-driven three-component cycliza-
tion that enables the direct synthesis of pyri
mido[1,2-b]indazole derivatives 144 through
the in situ trapping of a 1,3-vinylimine ion in-
termediate. The reaction proceeds under mild
conditions from bromodifluoroacetic acid de-
rivatives 141, enaminones 142, and 3-amino
indazoles 143. Notably, this robust methodo
logy allows for the efficient incorporation of
aliphatic substituents and demonstrates ex-
cellent compatibility with structurally com-
plex bioactive molecules. This transformation
represents the first example of a photoinduced
multicomponent reaction employing bromodi
fluoroacetic acid derivatives as a C1 synthon.
The reactions were carried out in DMSO at
room temperature using fac-Ir(ppy)₃ (2 mol%)
as the photocatalyst under blue LED irradia-
tion for five hours. The desired pyrimido[1,2-b]
indazole products 144 were obtained in mod-
erate to good yields, ranging from 40% to 79%.
Despite their initial fluorinated structure, both
64 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
fluorine atoms from the bromodifluoroacetic
acid derivatives 141 are lost during the course
of the reaction. Nevertheless, fluorination is
retained through aromatic substitution on the
3-aminoindazole starting materials 143, which
is preserved in the final heterocyclic products
144. The resulting pyrimido[1,2-b]indazoles
144 offer structural diversity and potential
relevance in medicinal chemistry due to their
fused heterocyclic architecture and tunable
fluorine content.
Scheme 53. Preparation of pyrimido[1,2-b]indazole derivatives.
pyrimido[1,2-b]indazoles 144 offer structural diversity and potential relevance in medicinal
chemistry due to their fused heterocyclic architecture and tunable fluorine content.
Scheme 53. Preparation of pyrimido[1,2-b]indazole derivatives.
Manna and Prabhu (Scheme 54) [247] reported a visible-light-mediated three-component
difunctionalization of activated alkynes 145 using boronic acids 146 and hypervalent iodine
reagents 147, enabling the synthesis of 3-alkylated coumarins 148. The para-substituent on the aryl
ring of the aryl alkynoate was found to be crucial for directing selective chain alkylation, facilitating
coumarin formation under mild conditions. Reactions were performed in 1,2-dichloroethane (DCE)
at room temperature over 8–12 hours, employing Ru(bpy)3Cl2 (0.5 mol%) as the photocatalyst
under visible-light irradiation. The desired coumarin products 148 were obtained in yields of up to
60%. Fluorinated motifs were incorporated via mono-fluoro or trifluoromethyl substitutions on the
aromatic ring or within the ester/amide fragments of the starting alkynes 145, showcasing the
method’s compatibility with fluorinated substrates.
Scheme 54. Synthesis of coumarins.
CONCLUSIONS.
In sum, photochemistry reimagines light not as a passive illuminator but as a precise and sustainable
reagent—unlocking synthetic possibilities with elegance and minimal environmental cost. It is no
exaggeration to state that many of the reactions described in this review would be inaccessible
under conventional thermal, acid–base, or redox conditions. Photochemical activation enables
unique reactivity patterns, particularly through radical pathways, that allow for the rapid
construction of complex molecular architectures.
That said, photochemistry is not universally applicable. Certain structural targets and reactivity
types remain beyond theirreach, and the approach carries inherent limitations. One key challenge
lies in the architectural design of starting materials: the spatial arrangement and positioning of
reactive functional groups must be meticulously orchestrated to ensure productive radical
engagement. This requirement stems from the mechanistic nature of photochemical reactions,
which often proceed through highly selective and transient radical intermediates. Another limitation
is the labor-intensive optimization process. Small changes in reaction parameters—such as
pyrimido[1,2-b]indazoles 144 offer structural diversity and potential relevance in medicinal
chemistry due to their fused heterocyclic architecture and tunable fluorine content.
Scheme 53. Preparation of pyrimido[1,2-b]indazole derivatives.
Manna and Prabhu (Scheme 54) [247] reported a visible-light-mediated three-component
difunctionalization of activated alkynes 145 using boronic acids 146 and hypervalent iodine
reagents 147, enabling the synthesis of 3-alkylated coumarins 148. The para-substituent on the aryl
ring of the aryl alkynoate was found to be crucial for directing selective chain alkylation, facilitating
coumarin formation under mild conditions. Reactions were performed in 1,2-dichloroethane (DCE)
at room temperature over 8–12 hours, employing Ru(bpy)3Cl2 (0.5 mol%) as the photocatalyst
under visible-light irradiation. The desired coumarin products 148 were obtained in yields of up to
60%. Fluorinated motifs were incorporated via mono-fluoro or trifluoromethyl substitutions on the
aromatic ring or within the ester/amide fragments of the starting alkynes 145, showcasing the
method’s compatibility with fluorinated substrates.
Scheme 54. Synthesis of coumarins.
CONCLUSIONS.
In sum, photochemistry reimagines light not as a passive illuminator but as a precise and sustainable
reagent—unlocking synthetic possibilities with elegance and minimal environmental cost. It is no
exaggeration to state that many of the reactions described in this review would be inaccessible
under conventional thermal, acid–base, or redox conditions. Photochemical activation enables
unique reactivity patterns, particularly through radical pathways, that allow for the rapid
construction of complex molecular architectures.
That said, photochemistry is not universally applicable. Certain structural targets and reactivity
types remain beyond theirreach, and the approach carries inherent limitations. One key challenge
lies in the architectural design of starting materials: the spatial arrangement and positioning of
reactive functional groups must be meticulously orchestrated to ensure productive radical
engagement. This requirement stems from the mechanistic nature of photochemical reactions,
which often proceed through highly selective and transient radical intermediates. Another limitation
is the labor-intensive optimization process. Small changes in reaction parameters—such as
Manna and Prabhu (Scheme 54) [247] re-
ported a visible-light-mediated three-compo-
nent difunctionalization of activated alkynes
145 using boronic acids 146 and hypervalent
iodine reagents 147, enabling the synthesis
of 3-alkylated coumarins 148. The para-sub-
stituent on the aryl ring of the aryl alkynoate
was found to be crucial for directing selective
chain alkylation, facilitating coumarin forma-
tion under mild conditions. Reactions were
performed in 1,2-dichloroethane (DCE) at
room temperature over 8–12 hours, employing
Ru(bpy)3Cl2 (0.5 mol%) as the photocatalyst
under visible-light irradiation. The desired
coumarin products 148 were obtained in yields
of up to 60%. Fluorinated motifs were incorpo-
rated via mono-fluoro or trifluoromethyl sub-
stitutions on the aromatic ring or within the
ester/amide fragments of the starting alkynes
145, showcasing the method’s compatibility
with fluorinated substrates.
Scheme 54. Synthesis of coumarins.
65https://ucj.org.ua
Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
CONCLUSIONS.
In sum, photochemistry reimagines light
not as a passive illuminator but as a precise
and sustainable reagent—unlocking synthetic
possibilities with elegance and minimal envi-
ronmental cost. It is no exaggeration to state
that many of the reactions described in this re-
view would be inaccessible under conventional
thermal, acid–base, or redox conditions. Pho-
tochemical activation enables unique reactivi-
ty patterns, particularly through radical path-
ways, that allow for the rapid construction of
complex molecular architectures.
That said, photochemistry is not universally
applicable. Certain structural targets and reac-
tivity types remain beyond theirreach, and the
approach carries inherent limitations. One key
challenge lies in the architectural design of start-
ing materials: the spatial arrangement and po-
sitioning of reactive functional groups must be
meticulously orchestrated to ensure productive
radical engagement. This requirement stems
from the mechanistic nature of photochemical
reactions, which often proceed through highly
selective and transient radical intermediates.
Another limitation is the labor-intensive op-
timization process. Small changes in reaction
parameters—such as photocatalyst identity,
light source, solvent, or additives—can dra-
matically affect the outcome. The search for
ideal conditions can be extensive, yet when
successful, photochemical methods offer un-
matched efficiency, functional group tolerance,
and scalability. Most reactions proceed under
ambient conditions and require only cataly
tic amounts of photocatalyst, typically around
1 mol%, simplifying product isolation and
purification. Fluorination plays a prominent
role in many of these transformations. Fluo-
rine is introduced in diverse forms, including
mono-fluoro, trifluoromethyl, perfluoroalkyl,
trifluoromethoxy, and pentafluorosulfanyl
groups. Fluorinated reagents are frequently
employed, and multiple fluorine substitutions
are often retained in the final products. This
versatility makes photochemical synthesis par-
ticularly valuable for constructing fluorinat-
ed heterocycles with relevance to medicinal
chemistry and pharmaceutical development.
Notably, asymmetric photochemical transfor-
mations remain underexplored. The scarcity
of enantioselective protocols suggests that this
field is still in its early stages. Given the impor-
tance of chiral fluorinated compounds in drug
design, future research is expected to focus
on enantiocontrolled photochemical metho
dologies for fluorinated heterocyclic scaffolds.
Overall, photochemistry represents a vibrant
and rapidly evolving area of synthetic research,
offering vast potential for innovation. As the
field continues to expand, we anticipate excit-
ing developments that will further redefine the
boundaries of molecular construction.
AUTHORS’ CONTRIBUTION. All authors
have read the research results and approved
the final version of the manuscript.
CONFLICT OF INTEREST. The authors de-
clare no conflict of interest.
ACKNOWLEDGMENTS. We grate-
fully acknowledge the financial support
from IKERBASQUE, Basque Foundation
for Science (for Soloshonok). The authors
acknowledge the assistance of Microsoft
Copilot and Google Gemini for their sup-
port in translating to Ukrainian.
66 ISSN 2708-129X. Укр. хім. журн., 2026
RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review).ORGANIC CHEMISTRY
ОСТАННІ ДОСЯГНЕННЯ У ФОТОХІМІЧНИХ
ПІДХОДАХ ДЛЯ ОТРИМАННЯ
ФТОРОВМІСНИХ ГЕТЕРОЦИКЛІВ (огляд)
Аліція Взорек,1 Таїзо Оно,2
Даніель Беккер,3 Вей Чжан,4
Вадим А. Солошонок,5*
1 Хімічний інститут, Університет Яна
Кохановського в Кельці,
вул. Університетська 7, 25-406 Кельце,
Польща;
2 Національний інститут передової науки
та технологій (AIST),
2266-98, Анагахора, Шімошідамі, район
Моріяма, Нагоя, 463-8560, Японія;
3 Відділ фармацевтичної та лікарської
хімії, Фармацевтичний інститут,
Вільний університет Берліна,
Кьоніґін-Луїзе-Штрасе 2+4, 14195 Берлін,
Німеччина;
4 Хімічний факультет, Університет
Массачусетса в Бостоні, Бостон,
Массачусетс 02125, Сполучені Штати
Америки;
5 ІКЕРБАСКЕ, Баскська наукова фундація,
вул. Марія Діас де Харо 3, Площа Бізкая,
48013 Більбао, Іспанія,
e-mail: vadimsoloshonok@gmail.com
Анотація: Фторовмісні гетероцикли за-
ймають центральне місце у фармацевти-
ці, агрохімії та матеріалознавстві завдяки
своїм унікальним фізико-хімічним власти-
востям та широкій функціональній значу-
щості. Прагнення до ефективних та еколо-
гічно стійких методів синтезу сприяло поя-
ві фотохімії як переконливої альтернативи
традиційним підходам на основі термічної,
кислотно-лужної чи окисно-відновної ре-
акцій. Дійсно, багато із трансформацій, ви-
світлених у цьому огляді, були б недосяж-
ними за звичайних умов, що підкреслює
виняткову реакційну здатність, яку забез-
печують процеси, що приводяться в рух
світлом.
Цей огляд вивчає ключові досягнення за
останнє десятиліття у фотохімічному син-
тезі фторованих гетероциклічних сполук.
Він починається з огляду фундаментальних
фотохімічних принципів і фотокаталізато-
рів, які використовують найчастіше. Потім
обговорення продовжується, розподіляю-
чи реакції на унімолекулярні, бімолекуляр-
ні та тримолекулярні класи. Унімолекулярні
реакції, як правило, включають циклізацію
стратегічно розроблених субстратів, здат-
них утворювати гетероциклічні структури
після фотоактивації. Бімолекулярні реакції
є найпоширенішим класом, де дві окремі
компоненти надають взаємодоповнюючі
фрагменти для побудови цільового гете-
роциклу. Натомість тримолекулярні фото-
хімічні реакції є надзвичайно рідкісними
через властиві механістичні, кінетичні та
просторові обмеження, пов’язані з тритіль-
ними взаємодіями в фотохімічних умовах.
Для кожної обговорюваної трансфор-
мації ми детально описуємо використаний
фотокаталізатор, джерело опромінення,
умови реакції та специфічний введений
патерн фторування. Фотохімія переосмис-
лює світло не просто як джерело енергії, а
як точний і стійкий реагент, що відкриває
синтетичні шляхи зі зручністю, селектив-
ністю та мінімальним впливом на довкілля.
Ця робота має на меті слугувати всебіч-
ним ресурсом для дослідників і практиків,
які прагнуть використовувати фотохімічні
67https://ucj.org.ua
Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim A. Soloshonok UCJ № 2/ Vol. 92
стратегії для синтезу фторованих гетеро-
циклів, з акцентом на каталітичну ефектив-
ність, структурну різноманітність та еколо-
гічну відповідальність.
Ключові слова: хімія фтору, гетероци-
кли, органофтористі сполуки, фото-редокс
каталіз, структурне різноманіття, зелена хі-
мія, сталий синтез, вплив на довкілля.
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Стаття надійшла: 30.01.2026
Стаття прийнята до друку: 01.03.2026
Стаття опублікована: 25.03.2026
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| id | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-768 |
| institution | Ukrainian Chemistry Journal |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-07-23T01:14:17Z |
| publishDate | 2026 |
| publisher | V.I.Vernadsky Institute of General and Inorganic Chemistry |
| record_format | ojs |
| resource_txt_mv | ucjorgua/11/f76c79d5c232f7c811c2d330134e9a11.pdf |
| spelling | oai:ojs2.1444248.nisspano.web.hosting-test.net:article-7682026-07-22T08:23:57Z RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review). Wzorek, Alicja Ono, Taizo Baecker, Daniel Zhang, Wei Soloshonok, Vadim Fluorine Chemistry, Heterocycles, Organofluorine Compounds, Photoredox Catalysis, Structural Diversity, Green Chemistry, Sustainable Methodologies, Environmental Impact. Fluorine-containing heterocycles occupy a central position in pharmaceutical, agrochemical, and materials science due to their unique physicochemical properties and broad functional relevance. The pursuit of efficient and sustainable synthetic methodologies has catalyzed the emergence of photochemistry as a compelling alternative to conventional thermal, acid–base, or redox-based approaches. Indeed, many of the transformations highlighted in this review would be unattainable under traditional reaction conditions, underscoring the distinctive reactivity enabled by light-driven processes. This review surveys key advances over the past decade in the photochemical synthesis of fluorinated heterocyclic compounds. It begins with an overview of fundamental photochemical principles and the most commonly employed photocatalysts. The discussion then proceeds to categorize reactions into unimolecular, bimolecular, and trimolecular classes. &nbsp;Unimolecular (intramolecular) reactions typically involve the cyclization of strategically designed substrates capable of forming heterocyclic frameworks upon photoactivation. Unimolecular (intramolecular) reactions represent the most prevalent class, wherein two distinct components contribute complementary fragments to construct the target heterocycle. Trimolecular (three-component) photochemical reactions, by contrast, are exceedingly rare due to the inherent mechanistic, kinetic, and spatial constraints associated with three-body interactions under photochemical conditions. For each transformation discussed, we detail the photocatalyst employed, the irradiation source, reaction conditions, and the specific fluorination pattern introduced. Photochemistry redefines light not merely as an energy source but as a precise and sustainable reagent—unlocking synthetic pathways with elegance, selectivity, and minimal environmental impact. This work aims to serve as a comprehensive resource for researchers and practitioners seeking to harness photochemical strategies for the synthesis of fluorinated heterocycles, with an emphasis on catalytic efficiency, structural diversity, and ecological responsibility. V.I.Vernadsky Institute of General and Inorganic Chemistry 2026-03-25 Article Article Physical chemistry Физическая xимия Фізична xімія application/pdf https://ucj.org.ua/index.php/journal/article/view/768 10.33609/2708-129X.92.2.2026.26-82 Ukrainian Chemistry Journal; Vol. 92 No. 2 (2026): Ukrainian Chemistry Journal; 26-82 Украинский химический журнал; ##issue.vol## 92 ##issue.no## 2 (2026): Ukrainian Chemistry Journal; 26-82 Український хімічний журнал; Том 92 № 2 (2026): Ukrainian Chemistry Journal; 26-82 2708-129X 2708-1281 en https://ucj.org.ua/index.php/journal/article/view/768/402 Copyright (c) 2026 Alicja Wzorek, Taizo Ono, Daniel Baecker, Wei Zhang, Vadim Soloshonok https://creativecommons.org/licenses/by-nc/4.0 |
| spellingShingle | Wzorek, Alicja Ono, Taizo Baecker, Daniel Zhang, Wei Soloshonok, Vadim RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review). |
| title | RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review). |
| title_full | RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review). |
| title_fullStr | RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review). |
| title_full_unstemmed | RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review). |
| title_short | RECENT ADVANCES IN PHOTOCHEMICAL SYNTHESIS OF FLUORINE-CONTAINING HETEROCYCLES (review). |
| title_sort | recent advances in photochemical synthesis of fluorine-containing heterocycles (review). |
| topic_facet | Fluorine Chemistry Heterocycles Organofluorine Compounds Photoredox Catalysis Structural Diversity Green Chemistry Sustainable Methodologies Environmental Impact. |
| url | https://ucj.org.ua/index.php/journal/article/view/768 |
| work_keys_str_mv | AT wzorekalicja recentadvancesinphotochemicalsynthesisoffluorinecontainingheterocyclesreview AT onotaizo recentadvancesinphotochemicalsynthesisoffluorinecontainingheterocyclesreview AT baeckerdaniel recentadvancesinphotochemicalsynthesisoffluorinecontainingheterocyclesreview AT zhangwei recentadvancesinphotochemicalsynthesisoffluorinecontainingheterocyclesreview AT soloshonokvadim recentadvancesinphotochemicalsynthesisoffluorinecontainingheterocyclesreview |