Recent advances in amidyl radical-mediated photocatalytic direct intermolecular hydrogen atom transfer

• Hao-Sen Wang,
• Lin Li,
• Xin Chen,
• Jian-Li Wu,
• Kai Sun,
• Xiao-Lan Chen,
• Ling-Bo Qu and
• Bing Yu

Beilstein J. Org. Chem. 2025, 21, 1306–1323, doi:10.3762/bjoc.21.100

• with a systematic understanding and strategic toolkit, thereby propelling the development of direct functionalization of C–H, B–H, Si–H, and Ge–H techniques in modern organic synthesis. Most of the photocatalysts used in this review are listed in Figure 3. Review Amidyl radical from N–H bond cleavage N

• cycloalkenes and alcohols. To eliminate the need for noble metal photocatalysts in the system, Duan’s group employed 2,4,5,6-tetra-9H-carbazol-9-yl-1,3-benzenedicarbonitrile (4CzIPN) as a metal-free photocatalyst (Scheme 3) [71]. This system initiated the formation of amidyl radical 20 from HRP-3 through a

• to produce amidyl radicals and oxygen anions in the presence of photocatalysts activated by visible light. Two representative cases illustrating this approach were reported in 2023. Building upon the experiments conducted by Alexanian’s group, Yan’s group extended the applicability of carborane as a

Recent advances in oxidative radical difunctionalization of N-arylacrylamides enabled by carbon radical reagents

• Jiangfei Chen,
• Yi-Lin Qu,
• Ming Yuan,
• Xiang-Mei Wu,
• Heng-Pei Jiang,
• Ying Fu and
• Shengrong Guo

Beilstein J. Org. Chem. 2025, 21, 1207–1271, doi:10.3762/bjoc.21.98

• particularly noteworthy for its use at room temperature, requiring no transition metals, photocatalysts, or additives. Notably, Umemoto's reagent served as the trifluoromethyl source, and the reaction was facilitated under blue LED irradiation, achieving good to excellent yields. Moreover, this approach

Biobased carbon dots as photoreductants – an investigation by using triarylsulfonium salts

• Valentina Benazzi,
• Arianna Bini,
• Ilaria Bertuol,
• Mariangela Novello,
• Federica Baldi,
• Matteo Hoch,
• Alvise Perosa and
• Stefano Protti

Beilstein J. Org. Chem. 2025, 21, 1024–1030, doi:10.3762/bjoc.21.84

• biocompatibility. The electrochemical properties of such materials have been then evaluated by cyclic voltammetry (CV). For all the properties mentioned above, CDs emerged as low-cost and sustainable photocatalysts. Indeed, upon visible-light irradiation, the generated excited state CD* can operate as either

Study of tribenzo[b,d,f]azepine as donor in D–A photocatalysts

• Katy Medrano-Uribe,
• Jorge Humbrías-Martín and
• Luca Dell’Amico

Beilstein J. Org. Chem. 2025, 21, 935–944, doi:10.3762/bjoc.21.76

• great applicability in the field of photocatalysis. Most of these compounds are based on complex D–A–D structures or multi-D–A systems, such as 4CzIPN. Whereas these systems have been widely studied and applied as photocatalysts, simpler D–A structures remain less explored. Nevertheless, the simplicity

• powerful tool for the construction and functionalization of organic molecules and materials. Thus, the scientific community has focused on the design and study of new organic molecules that can be used as photocatalysts, replacing generally more expensive metal-based complexes [1][2][3]. Furthermore, there

• is a particular interest in the obtainment of organic molecules with well-balanced redox potentials in the excited state that can act as bimodal photocatalysts, facilitating their use in oxidative and reductive quenching cycles. In this sense, it is crucial to understand the molecule's structure

Light-enabled intramolecular [2 + 2] cycloaddition via photoactivation of simple alkenylboronic esters

• Lewis McGhie,
• Hannah M. Kortman,
• Jenna Rumpf,
• Peter H. Seeberger and
• John J. Molloy

Beilstein J. Org. Chem. 2025, 21, 854–863, doi:10.3762/bjoc.21.69

• be derivatized to demonstrate the synthetic utility of the process. Although reactivity is currently limited to intramolecular quenching, it is envisaged the developed insights will serve as a blueprint for future endeavors to achieve sensitization using high energy photocatalysts, especially when

Photocatalyzed elaboration of antibody-based bioconjugates

• Marine Le Stum,
• Eugénie Romero and
• Gary A. Molander

Beilstein J. Org. Chem. 2025, 21, 616–629, doi:10.3762/bjoc.21.49

• catalysts, including photoredox catalysts, energy-transfer catalysts, and genetically encoded photocatalysts, highlighting their distinct features, mechanisms, applications, and prospects [41]. This thorough analysis showcased the promising advancements in the chemical modification of proteins. As this

• selectivity and the preservation of sensitive biological structures when appropriate redox potentials of photocatalysts are applied to the targeted amino acid. Additional advantages of photoinduced reactions include the ability to perform the reactions rapidly (typically <15 minutes). It was only in the late

• the light, the lamp wattage, and diverse photocatalysts or mechanisms (e.g., energy transfer, photoredox, or electron-donor/electron-acceptor photoinduced electron transfer) might all be brought to bear on controlling the DAR. In addition to the DAR, homogeneity for conjugation at specific sites using

Photomechanochemistry: harnessing mechanical forces to enhance photochemical reactions

• Francesco Mele,
• Ana M. Constantin,
• Andrea Porcheddu,
• Raimondo Maggi,
• Giovanni Maestri,
• Nicola Della Ca’ and
• Luca Capaldo

Beilstein J. Org. Chem. 2025, 21, 458–472, doi:10.3762/bjoc.21.33

• transform molecules. Intriguingly, photocatalysts typically absorb harmless visible light and can be chosen ad hoc to trigger the desired chemistry. Indeed, the photocatalyst–substrate interaction can occur via energy transfer [4][5][6][7][8], single-electron transfer [9][10][11][12], or hydrogen-atom

• insoluble reagents and/or photocatalysts. Additionally, as discussed, the use of impact forces can lead to unique selectivity profiles compared to solution-based methods, further enhancing its utility. Thirdly, dissolved oxygen must be often meticulously removed in solution-based methods via tedious

Beyond symmetric self-assembly and effective molarity: unlocking functional enzyme mimics with robust organic cages

• Keith G. Andrews

Beilstein J. Org. Chem. 2025, 21, 421–443, doi:10.3762/bjoc.21.30

• of increasing importance in the search for sustainable feedstocks, and cages that organize and polarize have advantages in this precise reactivity. The need for polarization may be circumvented by incorporating photocatalysts into cages [183][429], which are also likely to provide novel site

• -selective reactions [21][185][430][431][432][433]. Cage structure may also activate photocatalysts [434] or help restrict detrimental photocatalyst deactivation reactions [435]. We also point towards conformational autodesymmetrization [39] as a largely ignored strategy to develop low-symmetry cavities

Red light excitation: illuminating photocatalysis in a new spectrum

• Lucas Fortier,
• Corentin Lefebvre and
• Norbert Hoffmann

Beilstein J. Org. Chem. 2025, 21, 296–326, doi:10.3762/bjoc.21.22

• advantageous for large-scale applications, offering enhanced safety and operational simplicity. Traditionally, research in this field has focused on metal-based photocatalysts, particularly those based on transition metals like ruthenium and osmium due to their intrinsic photophysical properties. However, with

• growing concerns around environmental sustainability, there is increasing interest in developing photocatalysts that are more accessible, tunable, and eco-friendly. Each section of this document discusses a specific approach to red-light photocatalysis, reflecting the field’s evolution and exploring

• diverse catalyst types and applications. The first section is dedicated to metal-based photocatalysts. Complexes involving metals such as osmium and ruthenium, have dominated red-light photoredox catalysis because of their ability to absorb low-energy photons and sustain redox cycles via stable excited

Emerging trends in the optimization of organic synthesis through high-throughput tools and machine learning

• Pablo Quijano Velasco,
• Kedar Hippalgaonkar and
• Balamurugan Ramalingam

Beilstein J. Org. Chem. 2025, 21, 10–38, doi:10.3762/bjoc.21.3

• heterogeneous solid–liquid reactions. In their report, they described the reaction slugs as serial microbatch reactors (SMBRs) separated through gas segments that incorporated liquid reagents and solid photocatalysts in a continuous flow. The slugs were generated by establishing a stable gas–liquid segmented

Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts

• Mandeep K. Chahal

Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257

• , photocatalysts, and electrocatalysts are presented here. The effect of macrocyclic structural modifications such as their functionalization with different substituents, distortion from planarity, conformational flexibility and rigidity towards catalytic activity are presented, highlighting the potential of these

• photocatalysts. The results demonstrated that these substituents significantly influenced the redox properties of the porphyrins, yielding up to 86% with the electron-poor meso-tetrakis(pentafluorophenyl)porphyrin (67), compared to H2TPP and other electron-rich systems. This finding indicated that fine-tuning

• macrocycles as photocatalysts in organic synthesis, involving both single electron transfer (SET) and energy transfer (ET) mechanistic approaches [84]. This review does not only focus on the metal-free porphyrin macrocycles, but it also covers the area of different porphyrinoid systems, such as heteroatom

Recent advances in transition-metal-free arylation reactions involving hypervalent iodine salts

• Ritu Mamgain,
• Kokila Sakthivel and
• Fateh V. Singh

Beilstein J. Org. Chem. 2024, 20, 2891–2920, doi:10.3762/bjoc.20.243

• Morita–Baylis–Hillman (MBH) acetates using a variety of diaryliodonium triflates [65]. The reaction was carried out with MBH acetate 33 and diphenyliodonium triflate 16 in the presence of different photocatalysts and bases. Methylene blue trihydrate (MB·3H2O) was identified as a highly active

Transition-metal-free synthesis of arylboronates via thermal generation of aryl radicals from triarylbismuthines in air

• Yuki Yamamoto,
• Yuki Konakazawa,
• Kohsuke Fujiwara and
• Akiya Ogawa

Beilstein J. Org. Chem. 2024, 20, 2577–2584, doi:10.3762/bjoc.20.216

• of photocatalysts or UV light irradiation without metal catalysts [45][46][47][48]. Similar homolysis by electrolysis has also been reported [49]. These two activation methods required special equipment (i.e., light sources or electronic devices). To achieve thermal homolysis of the Ar–Bi bonds, the

• aryl radicals without photocatalysts, and the trapping with diselenides afforded a variety of diaryl selenides [59]. Based on these backgrounds of our studies and the fundamental property, i.e., the weak bond dissociation energy of the Ph–Bi bond (46 kcal/mol) [60], we hypothesized that aryl radicals

Visible-light-mediated flow protocol for Achmatowicz rearrangement

• Joachyutharayalu Oja,
• Sanjeev Kumar and
• Srihari Pabbaraja

Beilstein J. Org. Chem. 2024, 20, 2493–2499, doi:10.3762/bjoc.20.213

• File 1, Table S1, entries 4–6) however, when the time was increased there was minimal enhancement in yield (see details in Supporting Information File 1, Table S1, entry 2). Following additional adjustment of the reaction conditions with various solvents, oxidants, lights, and photocatalysts, (see

Photoredox-catalyzed intramolecular nucleophilic amidation of alkenes with β-lactams

• Valentina Giraldi,
• Giandomenico Magagnano,
• Daria Giacomini,
• Pier Giorgio Cozzi and
• Andrea Gualandi

Beilstein J. Org. Chem. 2024, 20, 2461–2468, doi:10.3762/bjoc.20.210

• photocatalysts (PC) that act as oxidants in the excited state [27]. The direct functionalization of amides with alkenes has been a relatively underexplored area in research, as evidenced by the limited number of examples reported in the literature. An interesting observation was made by the Nicewicz group during

A facile three-component route to powerful 5-aryldeazaalloxazine photocatalysts

• Ivana Weisheitelová,
• Radek Cibulka,
• Marek Sikorski and
• Tetiana Pavlovska

Beilstein J. Org. Chem. 2024, 20, 1831–1838, doi:10.3762/bjoc.20.161

• -deazaflavins [11][12][13]. Recently, it has been discovered that both 5-deazaflavins 1 and 5-deazaalloxazines 2, which have an aryl substituent in position C(5), form stable radicals that act as powerful reductive photocatalysts with a reducing power comparable to that of lithium [E*(1/1•) = −3.3 V vs SCE

• of photocatalysts by tuning their redox and photophysical properties. Thus, we successfully developed a one-pot, three-component synthetic method with those substituents in 5-aryldeazaflavins 1 on the deazaisoalloxazine core or on the phenyl ring by condensation of N-substituted anilines, aromatic

• substituents at positions 7 and 8 of the deazaalloxazine ring (see Figure 1 for numeration) showed the best reactivity as reductive photocatalysts. Such an outcome of MCR opens up the possibility of their production on a larger scale for commercial needs. However, the synthesis of the 7- and 8-methoxy

Hetero-polycyclic aromatic systems: A data-driven investigation of structure–property relationships

• Sabyasachi Chakraborty,
• Eduardo Mayo Yanes and
• Renana Gershoni-Poranne

Beilstein J. Org. Chem. 2024, 20, 1817–1830, doi:10.3762/bjoc.20.160

• molecules have been used in diverse settings, functioning as organic field effect transistors [10][11][12], light-emitting diodes [13][14][15], organic semiconductors [16][17], organic photovoltaics [1][18][19][20][21][22], photocatalysts [23], and biological agents for tracking or inhibition [24][25], and

Benzylic C(sp³)–H fluorination

• Alexander P. Atkins,
• Alice C. Dean and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 1527–1547, doi:10.3762/bjoc.20.137

• -fluorobenzoates as both photocatalysts or photo-auxiliaries and was demonstrated on a number of benzylic examples. Photochemical Photochemical methods have proven to be powerful tools in the generation of reactive intermediates, including benzylic radicals [64][65][66][67]. Oxidative photochemical

Generation of alkyl and acyl radicals by visible-light photoredox catalysis: direct activation of C–O bonds in organic transformations

• Mithu Roy,
• Bitan Sardar,
• Itu Mallick and
• Dipankar Srimani

Beilstein J. Org. Chem. 2024, 20, 1348–1375, doi:10.3762/bjoc.20.119

• photocatalysts, transition-metal photoredox catalysts, and metallaphotocatalysts to produce acyl and alkyl radicals driven by visible light. Keywords: acyl radical; alkyl radical; sustainable catalysis; visible light; Introduction The growing awareness of the necessity for sustainable developments has been

• . Different photocatalysts, such as transition metal complexes [23][24], organic dyes [25], and semiconductors [26], can be employed for visible-light-induced chemical processes. The choice of photocatalyst depends on the specific requirements of the catalytic process, including the type of reaction, the

• targeted absorption wavelength, and the overall efficacy. Researchers continue to explore and design photocatalysts to enhance the performance in various photocatalytic applications. Visible-light-induced photoredox catalysis has been used in a variety of chemical reactions, including C–C, C–N, C–O, and C

Mechanistic investigations of polyaza[7]helicene in photoredox and energy transfer catalysis

• Johannes Rocker,
• Till J. B. Zähringer,
• Matthias Schmitz,
• Till Opatz and
• Christoph Kerzig

Beilstein J. Org. Chem. 2024, 20, 1236–1245, doi:10.3762/bjoc.20.106

• Johannes Rocker Till J. B. Zahringer Matthias Schmitz Till Opatz Christoph Kerzig Department of Chemistry Johannes Gutenberg University, Duesbergweg 10–14, 55128 Mainz, Germany 10.3762/bjoc.20.106 Abstract Organic photocatalysts frequently possess dual singlet and triplet photoreactivity and a

• recent years was pioneered by the introduction of photocatalysts (PC) based on metals such as Ru and Ir [1][2][3][4][5][6]. However, due to the high cost and limited availability of precious metals, organic photocatalysts have become a focal point of academic and industrial research [7][8][9][10][11][12

• rule [43]. However, helicenes have not been broadly considered as potential photocatalysts or sensitizers or their applications were unsuccessful [44]. Recently, one of our groups exploited the highly reducing polyaza[7]helicene (Aza-H, see Scheme 1 for its structure) for sulfonylation/arylation three

SOMOphilic alkyne vs radical-polar crossover approaches: The full story of the azido-alkynylation of alkenes

• Julien Borrel and
• Jerome Waser

Beilstein J. Org. Chem. 2024, 20, 701–713, doi:10.3762/bjoc.20.64

• since it is known to be reduced by photocatalysts such as Cu(dap)2Cl [17]. This perfectly fits a catalytic cycle involving the reduction of Ts-ABZ (3) followed by oxidation of the carbon radical to form a carbocation and regenerate the ground state catalyst. Styrene (1a) was used as model substrate

• a non-complexed copper catalyst formed during the transformation [24][51]. When iridium-based photocatalysts were tested, no product formation or only traces were observed (Table 2, entries 2 and 3). Using Ru(bpy)3Cl2·6H2O afforded 17% of 4a, a similar yield as with Cu(dap)2Cl with a reduced

• except for 4ClDPAIPN which afforded 10% of yield of 4a (Table 2, entries 6–10). No correlation between the different redox potentials of the photocatalysts and the yield of the reaction could be established. Ru(bpy)3Cl2·6H2O was selected as the optimal catalyst since it afforded the highest yield and

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• ], have been employed as suitable photocatalysts (Scheme 4B). Under visible light irradiation the photocatalyst (PC) is excited into its corresponding excited state (*PC), where it can be reduced by a suitable electron donor such as DIPEA or Hantzsch ester to generate the reduced form of the photocatalyst

• , the aminodecarboxylation reaction proved unsuccessful when employing alternative photocatalysts such as Ru(bpy)3Cl2 or eosin Y, underscoring the distinctive ability of q-OAc to activate TCNHPI esters via EDA complex formation. Photoinduced transition metal-catalyzed mechanisms The in situ formation of

• significant advantages compared to other methods. It allows for single electron reduction to be facilitated by cost-effective carbon-based cathodes, eliminating the requirement for precious metal photocatalysts or exogeneous reductants such as Zn0. In the final section of this perspective, we explore examples

Visible-light-induced radical cascade cyclization: a catalyst-free synthetic approach to trifluoromethylated heterocycles

• Chuan Yang,
• Wei Shi,
• Jian Tian,
• Lin Guo,
• Yating Zhao and
• Wujiong Xia

Beilstein J. Org. Chem. 2024, 20, 118–124, doi:10.3762/bjoc.20.12

• radicals. This method allows the efficient synthesis of various indole derivatives without the need of photocatalysts or transition-metal catalysts. Mechanism experiments indicate that the process involves a radical chain process initiated by the homolysis of Umemoto's reagent. This straightforward method

• usually occur under mild conditions, they typically require expensive metal-based photocatalysts or structurally complex organic dyes [18]. Therefore, the development of a photoinduced cascade reaction without the need of additional catalysts or additives remains highly desirable [19]. The introduction of

• to furnish trifluoromethylated dihyropyrido[1,2-a]indolones under mild conditions, without the need of photocatalysts or transition metals [28]. Results and Discussion We initialized our study by employing Ru(bpy)3Cl2·6H2O and Umemoto’s reagent to generate trifluoromethyl radicals via a photo

Optimizing reaction conditions for the light-driven hydrogen evolution in a loop photoreactor

• Pengcheng Li,
• Daniel Kowalczyk,
• Johannes Liessem,
• Mohamed M. Elnagar,
• Dariusz Mitoraj,
• Radim Beranek and
• Dirk Ziegenbalg

Beilstein J. Org. Chem. 2024, 20, 74–91, doi:10.3762/bjoc.20.9

• in a proper way, solar energy can be converted to hydrogen fuels. Hydrogen as an energy carrier has zero carbon emission and a high energy density [11][12]. While significant efforts are directed towards developing effective photocatalysts for solar water splitting [13][14][15][16], a crucial

• the contrary, expanding photocatalytic systems, particularly those employing powdered photocatalysts, to a larger scale is notably more straightforward [17][18]. However, complications arise when attempting to scale up reactors solely based on geometric similarity, as alterations in mixing and

• , identifying photocatalysts capable of efficient performance across broad sunlight wavelength ranges proves to be a complex endeavor [26][27][28]. Therefore, artificial light sources are typically applied for lab testing of photocatalytic reactions. Compared to conventional light sources, light-emitting diodes