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

• source. Upon light irradiation, it can release an azide radical by homolysis of the I−N3 bond [46]. We were pleased to see that irradiation of a mixture of styrene (1a), Ph-EBX (2) and Ts-ABZ (3) afforded 17% isolated yield of the desired homopropargylic azide 4a (Table 1, entry 1). Heating the reaction

• generate a large quantity of iodanyl radical from Ts-ABZ (3) homolysis and from the addition–elimination on Ph-EBX (2). Since no quencher is present in the mixture, we wondered if the accumulation of those radicals could be responsible for the low yields obtained. Addition of (TMS)3SiH, a H• donor

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

• (PC•–) (Scheme 4A). This strong reducing agent mediates the one-electron reduction of the NHPI ester 10, forming radical anion intermediate 11. Fragmentation of 11 via N–O bond homolysis and decarboxylation forms the key tertiary radical 12 with concomitant formation of phthalimidyl anion (–Nphth) and

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

• , Umemoto’s reagent undergoes a homolysis process to generate the trifluoromethyl radical species. The trifluoromethyl radical is trapped by the terminal alkene and forms a relayed radical intermediate 6, which is intercepted by the indole ring realizing an intramolecular cyclization (6-exo-trig). The newly

• room temperature without additives. Mechanistic investigations support a photochemical process initiated by the homolysis of Umemoto's reagent under visible light irradiation. This method provides rapid access to a diverse range of trifluoromethylated dihydropyrido[1,2-a]indolone derivatives in

Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• ]. In a typical thiol–ene system, the polymerization undergoes a free-radical chain mechanism, involving an initiation step from a thiol group via radical transfer or homolysis (Scheme 11, initiation), radical addition of the thiyl radical to the ene functionality (propagation 1), transfer from the

• , such as organic peroxides, hydrogen peroxide, persulfates undergo homolysis of O–O bonds generating radicals that can break C–H bonds followed by a hydrogen abstraction reaction. Phenolic compounds can be oxidized by molecular oxygen in the presence of laccase, and the resulting phenolic radical reacts

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

• achieved (Scheme 1), showing that photolysis of stoichiometric Cu(II) chloride in the presence of unactivated alkenes allows for direct formation of vicinal dichloride products. The mechanistic study implicated initial formation of a chlorine radical through homolysis of a Cu–Cl bond via ligand-to-metal

• is proposed via thermal homolysis of a Mn(III) azide species and RLT from a second equivalent of Mn(III) azide furnishes the desired organic diazide, providing a strong demonstration of the applicability of RLT to not only photochemical but electrochemical conditions as well [35]. RLT in

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

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• ] (Scheme 36). One of the emerging areas in the chemistry of iodine(III) reagents with high synthetic potential is the visible-light induced I–O bond homolysis [152], which is currently employed mainly for the initiation of chain processes or stoichiometric oxidations, but definitely should find application

Simple synthesis of multi-halogenated alkenes from 2-bromo-2-chloro-1,1,1-trifluoroethane (halothane)

• Yukiko Karuo,
• Atsushi Tarui,
• Kazuyuki Sato,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2022, 18, 1567–1574, doi:10.3762/bjoc.18.167

• highly halogenated carbon centers, which enable halothane to participate in various reactions such as homolysis of carbon–halogen bonds and deprotonation. Multi-fluorinated compounds such as HCFC-133a (CF3CH2Cl) and HFC-134a (CF3CH2F) have been widely used in reactions with a variety of nucleophiles to

Synthesis of α-(perfluoroalkylsulfonyl)propiophenones: a new set of reagents for the light-mediated perfluoroalkylation of aromatics

• Durbis J. Castillo-Pazos,
• Juan D. Lasso and
• Chao-Jun Li

Beilstein J. Org. Chem. 2022, 18, 788–795, doi:10.3762/bjoc.18.79

• solubility of this class of molecules, perfluoroalkyl iodides have a tendency to be weakly soluble in common organic solvents (i.e., ethyl acetate and methanol) rendering their application troublesome [9]. Moreover, the homolysis of the perfluoroalkyl iodide produces iodine radicals that can result in stray

• -sulfonylpropiophenone moiety readily undergoes homolysis into three parts upon irradiation of light: a propiophenone radical – forming a stabilized and bulky “dummy group” –, a molecule of SO2, and our radical of interest. Once this radical is formed in solution, radical addition to the aromatic substrate undergoes

• in yields of 64% and 20%, respectively. Arenes containing halogens were attempted; however, in accordance to previous reported literature, the compounds were found to decompose under the ultraviolet radiation necessary for the homolysis of the reagent [25]. Lastly, some heteroaromatic substrates such

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

High-speed C–H chlorination of ethylene carbonate using a new photoflow setup

• Takayoshi Kasakado,
• Takahide Fukuyama,
• Tomohiro Nakagawa,
• Shinji Taguchi and
• Ilhyong Ryu

Beilstein J. Org. Chem. 2022, 18, 152–158, doi:10.3762/bjoc.18.16

• homolysis of the Cl–Cl bond to generate chlorine radicals. In a subsequent step, a SH2 reaction by chlorine radicals at C–H bonds generates alkyl radicals and HCl. The second SH2 reaction between alkyl radicals and molecular chlorine then occurs to give the C–H chlorinated product and a chlorine radical

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• isotope studies revealed the cleavage of the C(sp3)–H bond may be involved in the rate-determining step of this transformation. Mechanistically, prototypical homolysis of the peroxide in the presence of the Fe(II) catalyst will generate the alkyl radical 78 formed via hydrogen abstraction. The

• yield. After the prototypical homolysis of the peroxide in the presence of the Fe(II) catalyst, a silicon-centered radical 110 is formed via hydrogen abstraction. The addition of radical 110 across the alkene generates the alkyl radical intermediate 111. Oxidation of 111 by Fe(III)Ot-Bu delivers the

Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• . The mechanisms underlying photoredox catalysis of CuI complexes have special features and include ligand exchange and rebound mechanisms [38]. CuII complexes provide new avenues for photoredox catalysis, since CuII can undergo ligand exchange/light accelerated homolysis processes, which accelerates

• homolysis to produce CuI species and radical intermediates. These intermediates can initiate productive organic transformations [39]. 2.1 Visible-light-mediated Cu(I) catalytic cycle Upon the absorption of a photon (Scheme 4), CuILn forms a singlet MLCT state, which subsequently yields the excited triplet

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• the excited photocatalyst to the 5-IV complex resulted in excited 5-V. Subsequently, the homolysis of the Ni–Br bond in 5-V followed by a HAT process results in species 5-VI. The nickel–alkyl–aryl complex 5-VI undergoes reductive elimination to release the desired product 10a and regenerates the

• ]. Homolysis of the excited nickel(II) species 7-V results in the formation of a bromine radical, which then readily abstracts the allylic C(sp3)‒H to give the allylic radical species. Thus, the generated allylic radical species rebound to nickel complex and followed by reductive elimination delivers the

• the mechanistic studies, the authors proposed a catalytic cycle involving a triplet–triplet energy transfer between the excited iridium photocatalyst 17-II and nickel(II) complex 17-IV (Figure 17) [121]. The excited nickel(II) complex 17-V undergoes Ni‒Cl bond homolysis followed by a HAT event of the

Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes

• Suraj Patel,
• Tyson N. Dais,
• Paul G. Plieger and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2021, 17, 1518–1526, doi:10.3762/bjoc.17.109

• pathway involves electrophilic addition para to the phenol to form the ipso-substituted nitro 12 compound. Subsequent rearrangement of the nitro species 12 to the nitrito dienone 13, by homolysis and recombination of the radical pair, is followed by hydrolysis to furnish alcohol 6 [70]. Addition of the

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• the activation energies for both cis–trans-isomerization and for the transformation of vinylcyclopropanes into cyclopentenes. Both processes could occur by a C–C-bond homolysis to form a diradical. Computational studies by Gety, Hrovat, and Borden indicated that there would be a preference for

• -valent transition metals such as Pd(0) also have a valuable catalytic role, particularly because of their ability to participate in oxidative addition reactions and to form π-allyl complexes. In the absence of nucleophiles, homolysis of the distal C–C bond takes place under the effect of high temperature

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

• of vinylcyclopropanes with olefins [8]. The reaction mechanism of this cycloaddition process was similar to other thiyl radical-catalyzed cycloaddition cascade reactions. The alkylthiyl radical generated by the homolysis of a disulfide-bridged peptide precatalyst under UV-light irradiation triggers

• radical 17 (Mes–Acr–Ph•). The subsequent reaction of the formed styrene radical 16 with another styrene 18 gives the radical species 19 and the reoxidation of the acridine radical 17 by a thiyl radical, which is generated by the homolysis of diphenyl disulfide, regenerating the photocatalyst. In a

• decomposes into ketone or aldehyde products (Scheme 9). However, in the absence of light or oxygen, disulfide could not catalyze the oxidative cleavage of olefins. It was proposed that disulfide and the olefin might be able to form a charge-transfer complex, which may rationalize the unconventional homolysis

p-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies

• Panagiotis S. Gritzapis,
• Panayiotis C. Varras,
• Nikolaos-Panagiotis Andreou,
• Katerina R. Katsani,
• Konstantinos Dafnopoulos,
• George Psomas,
• Zisis V. Peitsinis,
• Alexandros E. Koumbis and
• Konstantina C. Fylaktakidou

Beilstein J. Org. Chem. 2020, 16, 337–350, doi:10.3762/bjoc.16.33

• DNA-photocleavers, and are proposed as new leads for “on demand” biotechnological applications in drug discovery and medicine. Keywords: DNA binding; DNA photocleavage; N–O homolysis; oxime carbamates; photocleavage agents; Introduction Small organic molecules able to bind DNA provide promises for

• , Figure 1) are also recognized as DNA “photocleavage” agents owing their action to the homolysis of their vulnerable N–O bond, at 312 nm [9][39][40][41][42][43] or 365 nm [44][45] yielding photogenerated carbonyloxyl radicals (CRs), which are able to cause oxidative DNA damage. We have recently reported

• gradual formation of one product. A theoretical photochemical dissociation study resulted to the observation that 12 has the ability to dissociate, as expected, with homolysis of its N–O bond overcoming very low energy barriers with high rate constants, on the contrary to 11, where its photochemical

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• , the homolysis of diphenyldiselenide 73 under heating conditions produces the phenylseleno radical 26 [93]. Then, the additon of radical 26 to the C–C double bond of MCPs derivatives 72 affords the radical intermediate 75 [94]. Next, the radical 75 goes through a ring-opening process to give the

• complex 126 is initially formed from the process of ligand exchange between the substrate and AgF2. The alkoxy radical 98 is produced via a single-electron oxidation by Ag–O bond homolysis. As a feature of the cyclopropane system, the radical 98 goes through a ring fission to form the alkyl radical 99

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• , homolysis of the C–C σ-bond in 60 provided the more stable hydroxyalkyl radical 61. This radical was oxidised by PIFA to yield the cationic intermediate 62, which finally lost a proton to furnish the reaction product. 1,2-Bis-trifluoromethylation of alkenes: Alkenes were efficiently and chemoselectively bis

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• quinazolinones. A putative mechanism involved the homolysis of DTBP to generate tert-butoxide radicals, which in turn abstracts a proton radical from the methyl(hetero)arene to facilitate the formation of a benzylic radical. The benzylic radical couples with o-aminobenzylamide to generate H. It then interacts

Synthesis of 2-oxindoles via 'transition-metal-free' intramolecular dehydrogenative coupling (IDC) of sp² C–H and sp³ C–H bonds

• Nivesh Kumar,
• Santanu Ghosh,
• Subhajit Bhunia and
• Alakesh Bisai

Beilstein J. Org. Chem. 2016, 12, 1153–1169, doi:10.3762/bjoc.12.111

• spectrum of biological and pharmacological properties and hence are very attractive as well as challenging synthetic targets [26]. Selected examples for the synthesis of 2-oxindole include an intramolecular homolytic aromatic substitution on the aryl ring by an amidyl radical formed by homolysis of a C–X

Copper-catalyzed aerobic radical C–C bond cleavage of N–H ketimines

• Ya Lin Tnay,
• Gim Yean Ang and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2015, 11, 1933–1943, doi:10.3762/bjoc.11.209

• the synthesis of azaheterocycles through an intramolecular N–C bond formation with the unsaturated systems [1][2][3][4][5][6]. As precursors of iminyl radicals, readily available oximes and their derivatives have commonly been utilized. The generation of iminyl radicals involves the homolysis of the N