Formaldehyde surrogates in multicomponent reactions

• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Bernhard Westermann

Beilstein J. Org. Chem. 2025, 21, 564–595, doi:10.3762/bjoc.21.45

• salts and TEMPO as the radical initiator/oxidant couple that promoted the intramolecular radical cyclization of suitable 1,3-dicarbonyl Ugi adducts 54 and 55 (Scheme 45) [108][109]. The stabilization of the enol in the 1,3-dicarbonyl Ugi adduct allows single-electron transfer (SET) with the anion

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

• in enhancing the mixing efficiency and increasing the exposure of the surface of the reaction mixture to light. Additionally, the formation of compound 8.2 was associated with the observation of an initial molten state of the mixture, which could have promoted single-electron-transfer processes that

Electrochemical synthesis of cyclic biaryl λ³-bromanes from 2,2’-dibromobiphenyls

• Andrejs Savkins and
• Igors Sokolovs

Beilstein J. Org. Chem. 2025, 21, 451–457, doi:10.3762/bjoc.21.32

• oxidation) and 6b (one-electron oxidation) into the respective bromine(III) species (Scheme 3C) [17] demonstrated a more similar behaviour to 6b suggesting that revealed oxidation is a single-electron-transfer process. It is important to note that this comparison assumes that the diffusion coefficients of

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

• unsaturated ring structure derived from squaric acid [47], has attracted attention due to its ability to promote single-electron transfer [48]. These compounds exhibit significant NIR fluorescence, making them valuable in applications such as biomolecule probing. Additionally, squaraine derivatives are well

• of these compounds in the field of photocatalysis [49]. The study has included a detailed mechanistic investigation to differentiate between competing single-electron transfer and energy transfer pathways. Through both experimental measurements and theoretical calculations, the authors have

• and mechanistic investigations of the near-IR-photocatalyzed aza-Henry reaction, the authors have proposed either a single-electron transfer or an energy transfer mechanism. Additionally, the reaction displayed an unexpected sensitivity to the light wavelength used. Employing a higher-energy light

Visible-light-promoted radical cyclisation of unactivated alkenes in benzimidazoles: synthesis of difluoromethyl- and aryldifluoromethyl-substituted polycyclic imidazoles

• Yujun Pang,
• Jinglan Yan,
• Nawaf Al-Maharik,
• Qian Zhang,
• Zeguo Fang and
• Dong Li

Beilstein J. Org. Chem. 2025, 21, 234–241, doi:10.3762/bjoc.21.15

• intermediate D via intramolecular radical cyclization. A single-electron-transfer (SET) process then occurred between the radical B and the radical D, resulting in the generation of cationic intermediate E, difluoroacetate anion and PhI. Finally, the product 3a was obtained after the deprotonation by

Recent advances in electrochemical copper catalysis for modern organic synthesis

• Yemin Kim and
• Won Jun Jang

Beilstein J. Org. Chem. 2025, 21, 155–178, doi:10.3762/bjoc.21.9

• electrochemistry and copper catalysis for various organic transformations. Keywords: copper; electrochemistry; radical chemistry; single-electron transfer; sustainable catalysis; Introduction Transition-metal-catalyzed cross-coupling has emerged as an effective method for forming carbon–carbon (C–C) and carbon

• viable alternatives to conventional chemical oxidizing and reducing agents [31], electrochemical reactions not only enable substrates to undergo single-electron transfer at the cathode or anode, either directly or indirectly, generating highly reactive radical intermediates, but also allow direct

• identical racemic carbonyl nucleophiles to generate Cu-enolate 44 and Ni-enolate 43 simultaneously (Figure 10). The Ni-enolate 43 undergoes anodic oxidation through single-electron transfer, releasing nickel-bound α-carbonyl radical 45, whereas the copper complex 44 remains electrochemically inert under

Cu(OTf)₂-catalyzed multicomponent reactions

• Sara Colombo,
• Camilla Loro,
• Egle M. Beccalli,
• Gianluigi Broggini and
• Marta Papis

Beilstein J. Org. Chem. 2025, 21, 122–145, doi:10.3762/bjoc.21.7

• or radical (Figure 1). The latter is typically operative when the reaction is carried out under oxidative conditions, usually in the presence of O2 and TEMPO, involving the formation of radical species through single-electron transfer (SET) from a copper catalyst to a precursor. Subsequent addition

• reaction proceeds through an initial single-electron transfer from NFBS assisted by the active copper species, followed by intermolecular hydrogen-atom transfer from the carbazate. The nitrogen radical intermediate I thus formed is decomposed into the acyl or alkyl radical intermediates II and III

Giese-type alkylation of dehydroalanine derivatives via silane-mediated alkyl bromide activation

• Perry van der Heide,
• Michele Retini,
• Fabiola Fanini,
• Giovanni Piersanti,
• Francesco Secci,
• Daniele Mazzarella,
• Timothy Noël and
• Alberto Luridiana

Beilstein J. Org. Chem. 2024, 20, 3274–3280, doi:10.3762/bjoc.20.271

• pathway for the functionalization of an electron-deficient olefin is the Giese reaction (Figure 1) [6][7]. This reaction involves the hydroalkylation of the olefin via radical addition (RA), followed by either hydrogen-atom transfer (HAT) or single-electron transfer (SET) and protonation. Traditionally

Hypervalent iodine-mediated intramolecular alkene halocyclisation

• Charu Bansal,
• Oliver Ruggles,
• Albert C. Rowett and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 3113–3133, doi:10.3762/bjoc.20.258

• ring attacks the activated alkene, if it is too electron-poor then it is not reactive enough. Moreover, if it is too electron-rich, then it preferentially oxidises via a single electron transfer mechanism which deactivates the ring as a nucleophile. The synthesis of fluorinated oxazepanes 36 was

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

• to absorb significant amounts of visible light photons, which allows them to reach an excited state. The excited porphyrin molecule is likely to undergo energy transfer (ET; photosensitization) or single-electron transfer (SET; photoredox catalysis) to substrate molecules (Figure 13). In

• initiated the reaction pathway. The authors proposed that under light irradiation, the porphyrin transitioned to its excited state, generating a phenyl radical through photoinduced single-electron transfer (Figure 15c). This phenyl radical then added to the furan (heteroarene), forming an aryl radical

• 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

Advances in radical peroxidation with hydroperoxides

• Oleg V. Bityukov,
• Pavel Yu. Serdyuchenko,
• Andrey S. Kirillov,
• Gennady I. Nikishin,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2024, 20, 2959–3006, doi:10.3762/bjoc.20.249

• oxidized by the excited photocatalyst to give the benzyl radical D and CO2. Further, single electron transfer from (Acr·-Mes) C to TBHP results in the ground state photocatalyst (Acr+-Mes) A and tert-butoxy radical E, which abstracts the hydrogen atom from TBHP to yield tert-butylperoxy radical F. The

• –peroxidation of alkenes 155 with TBHP and aldehydes 156 through visible-light photocatalysis was developed using fac-Ir(ppy)3 as the photoredox catalyst (Scheme 49) [113]. Under visible light irradiation, the excited state Ir(III)* is generated, and the single electron transfer of Ir(III)* with TBHP results in

• . Chlorine atom transfer from CHCl3 to the α-amino radical C results in the formation of the dichloromethyl radical D, which adds to styrene 180 to form the C-centered radical E. The authors further assume three possible pathways of the process. Pathway 1 involves single-electron transfer by Cu(II) to give

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

• the respective arylation product [50][51]. Lastly, arylation can occur through single-electron transfer (SET), where a cation radical obtained from aromatic hydrocarbons with high electron density yields the desired arylated product [52]. In this review article, we will provide a comprehensive

• state, eosin Y*. This excited state further undergoes oxidation via a single-electron-transfer (SET) reaction with Ar2IBF4 26, producing eosin Y+ and a phenyl radical 30 (Scheme 10). The radical intermediate 30 selectively binds to the C2 position of either quinoline or pyridine N-oxide, forming

Efficacy of radical reactions of isocyanides with heteroatom radicals in organic synthesis

• Akiya Ogawa and
• Yuki Yamamoto

Beilstein J. Org. Chem. 2024, 20, 2114–2128, doi:10.3762/bjoc.20.182

• quinoxaline synthesis was reported to proceed by irradiation with visible light in the presence of dibenzylamine ((PhCH2)2NH, MeCN, rt, blue LED) [64]. This reaction involves a visible-light-induced single electron transfer (SET) process. An efficient radical cascade cyclization has also been reported, in

Harnessing the versatility of hydrazones through electrosynthetic oxidative transformations

• Aurélie Claraz

Beilstein J. Org. Chem. 2024, 20, 1988–2004, doi:10.3762/bjoc.20.175

• formation of dimeric side products. Cyclic voltammetry analysis suggested an initial anodic single electron transfer (SET) to radical cation 5, cyclization and deprotonation. Subsequent SET oxidation in solution by 5 led to cation 7. Final deprotonation furnished aromatic cycle 4. In 2022, Zhang et al

Development of a flow photochemical process for a π-Lewis acidic metal-catalyzed cyclization/radical addition sequence: in situ-generated 2-benzopyrylium as photoredox catalyst and reactive intermediate

• Masahiro Terada,
• Zen Iwasaki,
• Ryohei Yazaki,
• Shigenobu Umemiya and
• Jun Kikuchi

Beilstein J. Org. Chem. 2024, 20, 1973–1980, doi:10.3762/bjoc.20.173

• intramolecular cyclization followed by proto-demetalation with trifluoroacetic acid (TFA). In catalytic cycle II, photoexcitation of the generated 2-benzopyrylium intermediates A under light irradiation facilitates single-electron transfer (SET) from benzyltrimethylsilane derivatives 2 as the donor molecule

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

• in the concerted transfer of an electron and a proton from the benzylic substrate resulting in the benzylic radical II – pathway [A] [67]. This radical can also be accessed via sequential oxidative single-electron-transfer (SET) and proton-transfer (PT) steps (pathway [B]), or concerted proton

• under the cell potentials required to initiate the first single-electron transfer, resulting in benzylic cation IV [89][90]. This species can then be captured by fluoride to give benzylic fluoride product V. HF·amine ionic liquids are a popular choice of fluoride source in organic electrochemistry as

Transition-metal-catalyst-free electroreductive alkene hydroarylation with aryl halides under visible-light irradiation

• Kosuke Yamamoto,
• Kazuhisa Arita,
• Masami Kuriyama and
• Osamu Onomura

Beilstein J. Org. Chem. 2024, 20, 1327–1333, doi:10.3762/bjoc.20.116

• intermediates through a single-electron transfer process [26][27][28][29][30][31]. In particular, electroreductive transformations have recently received renewed attention from modern synthetic chemists as a safer protocol than conventional methods using chemical reductants such as metal hydride species [32][33

Advancements in hydrochlorination of alkenes

• Daniel S. Müller

Beilstein J. Org. Chem. 2024, 20, 787–814, doi:10.3762/bjoc.20.72

• . The acridinium ion 161 now takes on the additional role of a phase-transfer catalyst, facilitating the transport of the chloride ion into the lipophilic alkene phase. Subsequently, under irradiation with blue LEDs, the acridinium cation 161 and the chloride anion engage in a single-electron-transfer

Enhanced reactivity of Li⁺@C₆₀ toward thermal [2 + 2] cycloaddition by encapsulated Li⁺ Lewis acid

• Hiroshi Ueno,
• Yu Yamazaki,
• Hiroshi Okada,
• Fuminori Misaizu,
• Ken Kokubo and
• Hidehiro Sakurai

Beilstein J. Org. Chem. 2024, 20, 653–660, doi:10.3762/bjoc.20.58

• thermal [2 + 2] cycloaddition. The [2 + 2] cycloaddition reactions of empty C60 have been known to proceed with unsaturated substrates having HOMO levels suitable for the thermal or photoinduced single-electron-transfer (SET) process (Scheme 1) [14][15][16][17][18][19][20][21][22][23]. Although the

Enhanced host–guest interaction between [10]cycloparaphenylene ([10]CPP) and [5]CPP by cationic charges

• Eiichi Kayahara,
• Yoshiyuki Mizuhata and
• Shigeru Yamago

Beilstein J. Org. Chem. 2024, 20, 436–444, doi:10.3762/bjoc.20.38

• stabilized by in-plane aromaticity, the single-electron transfer from [10]CPP to [5]CPP2+ to form [10]CPP•+⊃[5]CPP•+ is energetically unfavorable. The association constant (Ka) between [10]CPP⊃[5]CPP2+ [B(C6F5)4−]2 in 1,1,2,2-tetrachloroethane-d2 (TCE-d2) at 50 °C was determined to be 1.07 × 103 L·mol−1 by

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

• many applications as radical precursors. Mechanistically, NHPI esters undergo a reductive decarboxylative fragmentation to provide a substrate radical capable of engaging in diverse transformations. Their reduction via single-electron transfer (SET) can occur under thermal, photochemical, or

• absorption of light, an excited photocatalyst (*PC) engages in single-electron transfer (SET) with either donor (D) or acceptor (A) molecules (Scheme 3) [8][36]. Accordingly, a reductive quenching mechanism (path a) will operate when an excited photocatalyst effects the one-electron oxidation of a

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

• trifluoromethyl radical source under light irradiation. Umemoto’s reagent, which is capable of releasing a trifluoromethyl radical via a photoinduced single-electron-transfer (SET) process, is usually employed to enable the trifluoromethylation of unsaturated substrates [25][26][27]. Herein, we report a protocol

Recent advancements in iodide/phosphine-mediated photoredox radical reactions

• Tinglan Liu,
• Yu Zhou,
• Junhong Tang and
• Chengming Wang

Beilstein J. Org. Chem. 2023, 19, 1785–1803, doi:10.3762/bjoc.19.131

• smoothly delivered an electron donor–acceptor (EDA) complex II via coulombic interactions. Upon 456 nm blue LED light irradiation, the EDA complex II underwent a single electron transfer (SET) process, followed by subsequent decarboxylation to produce the alkyl radical intermediate A, accompanied by

• transformations, as depicted in Scheme 14. The dual-catalytic cycle comprised a photocatalytic cycle and a copper catalytic cycle, interconnected through an intermolecular single-electron transfer. Within the context of the photocatalytic cycle, the generation of the C(sp3)-centered alkyl radical A was

• depicted in Scheme 16. Initially, a photoactive EDA complex II was transiently formed through the combined action of NaI, PPh3, and the γ,σ-unsaturated phthalimide 33a. Upon irradiation with blue LEDs, the alkyl radical A was generated through a single-electron transfer from the iodide anion to the γ,σ

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• ·H2O, FeSO4, and Fe(acac)3 resulted in inferior chemical yields. Employment of 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) as a radical trapper inhibited the reaction, which proved that a radical process was involved. The reaction was initiated by a single electron transfer (SET) process from the