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

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• primary, secondary, and tertiary alkyl halides. The mechanistic investigation revealed the generation of a silyl–copper intermediate which activates the alkyl halides by a single electron transfer to form alkyl radical intermediates [54]. It was suggested that substituting B2pin2 for PhMe2Si-Bpin would

Visible-light-induced nickel-catalyzed α-hydroxytrifluoroethylation of alkyl carboxylic acids: Access to trifluoromethyl alkyl acyloins

• Feng Chen,
• Xiu-Hua Xu,
• Zeng-Hao Chen,
• Yue Chen and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2023, 19, 1372–1378, doi:10.3762/bjoc.19.98

• pivalic anhydride as activator to afford Ni(II) intermediate F. Subsequently, trapping of the alkyl radical C generates high-valent Ni(III) intermediate G, which undergoes facile reductive elimination to furnish the final coupling product 3 and Ni(I) intermediate H. The single-electron transfer (SET

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• bonds The possible mechanism of the CDC reaction involving ether α-C(sp3)–H bonds mainly follows the two pathways outlined in Scheme 2. Route a: First, the C(sp3)–H bond at the α-position of the oxygen atom undergoes a single-electron transfer under the combined action of the transition metal and an

• extract a hydrogen from the ether C (sp3)–H bond to form radicals. Subsequently, a single electron transfer (SET) leads to the oxonium species. Then, the enamine generated in situ from methyl aryl ketone and pyrrolidine undergoes a nucleophilic reaction with the oxonium species followed by hydrolysis to

• of the radical initiator to the ether to obtain the corresponding ether radical species. The coupling product is accessed through a single electron transfer (SET) and other transformations. In 2019, Tu et al. established a highly efficient Cu-catalyzed cross-dehydrogenative coupling to access a

Radical ligand transfer: a general strategy for radical functionalization

• David T. Nemoto Jr,
• Kang-Jie Bian,
• Shih-Chieh Kao and
• Julian G. West

Beilstein J. Org. Chem. 2023, 19, 1225–1233, doi:10.3762/bjoc.19.90

• Fe(II/III) cycle is proposed, where a single electron transfer from Fe(II) reduces the peroxyester and produces a carboxyl radical and Fe(III), which can coordinate an azide ligand. Rapid decarboxylation produces the transient alkyl radical which can be asymmetrically azidated by RLT from an Fe(III

Enabling artificial photosynthesis systems with molecular recycling: A review of photo- and electrochemical methods for regenerating organic sacrificial electron donors

• Grace A. Lowe

Beilstein J. Org. Chem. 2023, 19, 1198–1215, doi:10.3762/bjoc.19.88

Exploring the role of halogen bonding in iodonium ylides: insights into unexpected reactivity and reaction control

• Carlee A. Montgomery and
• Graham K. Murphy

Beilstein J. Org. Chem. 2023, 19, 1171–1190, doi:10.3762/bjoc.19.86

• cycloaddition reactions that occur without transition metal catalysts, the unexpected initiation of single electron transfer (SET) processes or photochemical transformations, and even proton transfers that appear to defy pKa limitations. The reaction pathways followed by iodonium ylides and Lewis basic reaction

• , they believed that the reaction was likely initiated by either single electron transfer between the reagents (not shown), or by electrophilic addition of the olefin onto the ylide, forming intermediate adduct 17. This was followed by formation of iodocycle 18, from which reductive elimination of

• as an electron donor–acceptor complex) [121], and this bonding description has recently been used to support proposals for single electron transfer (SET) reaction pathways between iodonium ylides and various halogen bond acceptors. Alternatively, halogen-bonded complexes of iodonium ylides could lead

Selective and scalable oxygenation of heteroatoms using the elements of nature: air, water, and light

• Damiano Diprima,
• Hannes Gemoets,
• Stefano Bonciolini and
• Koen Van Aken

Beilstein J. Org. Chem. 2023, 19, 1146–1154, doi:10.3762/bjoc.19.82

• separate” additives, a significant rate enhancement could be obtained with a positive impact on productivity rates. Results and Discussion There are a lot of similarities between electrochemistry and photoredox chemistry [33] as both rely on single-electron transfer processes to initiate reactions. In

• irradiation at 310 nm [27]. They concluded that both a single-electron transfer and a singlet oxygen path can occur depending on the nature of the compound. Intriguingly, the current method applies 365 nm irradiation at which thioanisole does not absorb (Supporting Information File 1, Figure S1). Also, the

• originates from water. In this tentative mechanism, the sulfide I forms with water and oxygen a photoactive complex II which is excited at 365 nm towards III. Via single-electron transfer both a radical cation IV and the superoxide V are generated. Subsequently, the sulfide radical cation IV undergoes a

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• Mattia Lepori Simon Schmid Joshua P. Barham Fakultät für Chemie und Pharmazie, Universität Regensburg, Universitatsstraße 31, 93040 Regensburg, Germany 10.3762/bjoc.19.81 Abstract Photoredox catalysis (PRC) is a cutting-edge frontier for single electron-transfer (SET) reactions, enabling the

• radicals that often provide access to new dimensions of synthetic chemical space, the field of single electron transfer (SET) in organic synthesis has expanded considerably in the past two decades. Among this area, photoredox catalysis (PRC) is highly attractive due to its abilities i) to generate reactive

Photoredox catalysis enabling decarboxylative radical cyclization of γ,γ-dimethylallyltryptophan (DMAT) derivatives: formal synthesis of 6,7-secoagroclavine

• Alessio Regni,
• Francesca Bartoccini and
• Giovanni Piersanti

Beilstein J. Org. Chem. 2023, 19, 918–927, doi:10.3762/bjoc.19.70

• manner due to their intrinsic mildness and broad substrate compatibility [16][17][18][19][20]. This transformative synthetic tool often utilizes direct single-electron transfer (SET) between an electronically excited photoredox catalyst and an organic substrate, resulting in oxidation or reduction, to

Sulfate radical anion-induced benzylic oxidation of N-(arylsulfonyl)benzylamines to N-arylsulfonylimines

• Joydev K. Laha,
• Pankaj Gupta and
• Amitava Hazra

Beilstein J. Org. Chem. 2023, 19, 771–777, doi:10.3762/bjoc.19.57

• single electron transfer (SET), is proposed to be involved in the plausible reaction mechanism. Keywords: arylsulfonylimine; benzylic oxidation; benzyl sulfonamide; K2S2O8; sulfate radical anion; Introduction Among various imine compounds [1], N-arylsulfonylimines are perhaps the most prominent due to

• abstraction (HAT) followed by single electron transfer (SET) enabled by the sulfate radical anion (SO4·−). Results and Discussion Initially, we investigated the reaction of N-benzenesulfonyl(benzyl)amine (1a) as a model substrate with K2S2O8 in MeCN at 80 °C for 12 h, conditions that were used earlier in our

• cleavage of the peroxy linkage under heating conditions [17]. The hydrogen atom is abstracted from the benzylic position of 1 by SO4·−, generating benzylic radical 1aa [14][15][16]. A single electron transfer (SET) could subsequently occur from 1aa to form the reactive species 1ab. Finally, the base