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

• catalysis in recent years not only with heavy metals such as ruthenium and iridium [1][2][3][4][5], but also with lighter elements [6][7][8]. This field of light-mediated organic transformations relies on the use of a photocatalyst to promote radical reactions through electron transfer between this former

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

• difluoroacetate anion. Conclusion In summary, we have successfully developed a sustainable and efficient method for synthesizing difluoromethylated and aryldifluoromethylated polycyclic imidazoles through visible-light-promoted radical reactions. In contrast to previous reports, we achieved high yields of

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

• reactions, particularly in controlling the high reactivity and selectivity of radical intermediates [13][14]. Early studies on copper-mediated radical reactions, such as Julia’s work on radical cyclization reaction [15], along with advancements in dimerization [16][17], oxidative cleavage [18][19], and

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

• . Keywords: C–H functionalization; oxidation; peroxidation; radical reactions; TBHP; Introduction Organic peroxides are used in many different areas of human activities. The traditional and most developed field is the use of peroxides as initiators in the polymerization process for the production of a wide

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

• the generation of aryl radicals, and the subsequent reaction with bis(pinacolato)diboron afforded a variety of arylboronates in moderate to good yields. Keywords: arylboronates; bis(pinacolato)diboron; radical reactions; transition-metal-free synthesis; triarylbismuthines; Introduction Arylboronates

• , the development of new synthetic methods of arylboronates using stable and versatile reagents under transition-metal-free conditions has recently attracted much attention [23][24][25][26][27]. In particular, the use of radical reactions has been considered as one of the effective methods, since

• diborons can capture the in situ-generated carbon-centered radicals [28][29][30][31][32][33][34][35][36]. Among the aryl sources in organic synthesis, triarylbismuthines are shelf-stable and easy-to-handle reagents with appropriate reactivities in transition-metal-catalyzed reactions and radical reactions

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

• methods. For these reasons, it is no exaggeration to say that radical reactions of group 17 interelement compounds with isocyanides have hardly been developed. Upon exposure to near-UV light, perfluoroalkyl iodides (RFI) undergo homolysis to form perfluoroalkyl radicals (RF•) and iodine radical (I•). The

• synthetic application has been discussed. A number of useful synthetic reactions have been developed from the reactions of group 15 and 16 heteroatom radicals with isocyanides. On the other hand, the use of other heteroatoms in radical reactions with isocyanides has been limited due to the limitations of

• group. Quinoline synthesis via aza-Bergman cyclization. Phenanthridine synthesis via radical cyclization of 2-isocyanobiaryls. Phenanthridine synthesis by radical reactions with AIBN, DBP and TTMSS. Phenanthridine synthesis by oxidative cyclization of 2-isocyanobiaryls. Phenanthridine synthesis using a

Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

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

• , initiating further radical reactions through the formation of radical cations B. Nucleophilic arylmethyl radicals C, which are generated from radical cations B by desilylation, undergo an addition reaction with 2-benzopyrylium intermediates A, giving rise to the corresponding radical cation. Catalytic cycle

1,2-Difluoroethylene (HFO-1132): synthesis and chemistry

• Liubov V. Sokolenko,
• Taras M. Sokolenko and
• Yurii L. Yagupolskii

Beilstein J. Org. Chem. 2024, 20, 1955–1966, doi:10.3762/bjoc.20.171

• 1,2-difluoroethylene (HFO-1132). The major routes for the preparation of the E- and Z-isomer of HFO-1132 are reviewed, along with the chemistry in radical, nucleophilic, and electrophilic reactions. Keywords: 1,2-difluoroethylene; fluorinated monomers; HFO-1132; hydrofluoroolefins; radical reactions

• reactions were not described at all. Nevertheless, the radical reactions are the most powerful instrument for the preparation of new molecules with a CHF–CHF fragment. For instance, the radical addition of hypohalites is a suitable high-yielding approach toward polyfluorinated aliphatic ethers and esters

Electrochemical radical cation aza-Wacker cyclizations

• Sota Adachi and
• Yohei Okada

Beilstein J. Org. Chem. 2024, 20, 1900–1905, doi:10.3762/bjoc.20.165

• piperidine 17 were obtained in good mass balance under non-electrochemical conditions. Although the detailed mechanism remains an open question, the electrochemical aza-Wacker cyclizations might be radical reactions rather than ionic ones, since the six-membered piperidine was not obtained from the

• . Synthetic outcomes and cyclic voltammetric studies suggest that the reactions are initiated by single-electron oxidation of the alkenes instead of the aryl sulfonamides. Although the detailed mechanism remains an open question, the electrochemical radical cation aza-Wacker cyclizations might be radical

• reactions rather than ionic ones, since five-membered pyrrolidine formation is preferred over six-membered piperidine formation. Further mechanistic studies of the electrochemical radical cation aza-Wacker cyclizations are underway in our laboratory. Experimental Electrochemical aza-Wacker cyclizations: The

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

• heightened by the current energy crisis and the adverse impacts of industrialization. The development of green and energy-efficient methods in organic chemistry that use renewable sources of starting materials is considered highly sustainable [1][2][3]. Radical reactions have profound applications in organic

• –halogen bond formation, as well as C–H functionalization [27]. Some notable examples include C–H arylation, various cross-coupling reactions, oxidative coupling, and photocatalytic radical reactions. The advantages of visible-light-induced photoredox catalysis are due to the ability to utilize visible

Advancements in hydrochlorination of alkenes

• Daniel S. Müller

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

• the case for radical reactions. According to these differences it is clear that applications of metal-promoted radical hydrochlorination reactions will mainly focus on complex molecules and substrates where classical hydrochlorination reactions fail. Carreira and Gaspar were the pioneers in reporting

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

• of parameters with which to control reactivity. In this perspective, we provide an overview of the different mechanisms for radical reactions involving NHPI esters, with an emphasis on recent applications in radical additions, cyclizations and decarboxylative cross-coupling reactions. Within these

• reaction classes, we discuss the utility of the NHPI esters, with an eye towards their continued development in complexity-generating transformations. Keywords: decarboxylative couplings; mechanisms; NHPI-esters; radical reactions; Introduction The historical challenges of using radicals in synthetic

• , which incorporate both radical and ionic bond-forming steps into a single synthetic operation [16][17]. The success of radical reactions is intimately linked to the mechanisms of their initiation and the radical progenitor employed. Amongst the many progenitors that are available, carboxylic acids are

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

• , numerous remarkable breakthroughs and notable progresses have been achieved in the realm of photoredox catalysis [1][2][3]. This domain has profoundly transformed modern organic synthesis, resulting in a considerable surge in research efforts centered on free radical reactions [4]. Presently, photoredox

• provided a more sustainable and economically viable approach but also demonstrated excellent performance in various transformations. It had been successfully applied to a series of radical reactions, including trifluoromethylation, deaminative alkylation, and asymmetric versions of Minisci reactions

• radical reactions. These reactions have garnered much attention due to their cost-effectiveness, low toxicity, and widespread availability. Notably, the NaI/PPh3 combined system has been successfully employed in the photofixation of nitrogen [51]. Despite these remarkable progresses made, there remain

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

• amenable to all radical generation approaches/substrate classes nor can they form all desired bonds from alkyl radical intermediates, limiting the toolkit of radical reactions. Recently, radical ligand transfer (RLT) [9][10][11] has emerged as a radical functionalization paradigm with the potential to

• and synthetic systems, radical ligand transfer (RLT) has reemerged as a powerful tool in the design of catalytic radical reactions. This development has been fueled by the unique aspects of RLT, with its ability to functionalize radicals with diverse nucleophilic reagents and inherent compatibility

NaI/PPh₃-catalyzed visible-light-mediated decarboxylative radical cascade cyclization of N-arylacrylamides for the efficient synthesis of quaternary oxindoles

• Dan Liu,
• Yue Zhao and
• Frederic W. Patureau

Beilstein J. Org. Chem. 2023, 19, 57–65, doi:10.3762/bjoc.19.5

• ethers and N-heteroarenes by using a novel catalytic system based on sodium iodide (NaI) and triphenylphosphine (PPh3), suggested to function as an electron donor–acceptor (EDA) complex [55][56][57][58][59][60]. Compared to previously reported radical reactions, this novel catalytic system has the key

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

• are a number of reviews on specific groups of redox-organocatalyzed oxidative transformations [43][44][45][46][47][48][49][50][51][52][53][54][55][56] and organocatalyzed enantioselective radical reactions were recently discussed [57]. However, the field remains not overviewed in general and it is not

Direct C–H amination reactions of arenes with N-hydroxyphthalimides catalyzed by cuprous bromide

• Dongming Zhang,
• Bin Lv,
• Pan Gao,
• Xiaodong Jia and
• Yu Yuan

Beilstein J. Org. Chem. 2022, 18, 647–652, doi:10.3762/bjoc.18.65

• the amidyl radical precursor under air is reported. A possible mechanism is proposed that proceeds via a radical reaction in the presence of CuBr and triethyl phosphite. Keywords: amination; copper; N-hydroxyphthalimides; radical reactions; triethyl phosphite; Introduction Practical methods for

Site-selective reactions mediated by molecular containers

• Rui Wang and
• Yang Yu

Beilstein J. Org. Chem. 2022, 18, 309–324, doi:10.3762/bjoc.18.35

• authors reported similar site-selective Diels–Alder reactions between 2 and inert aromatics including aceanthrylene and 1H-cyclopenta[l]phenanthrene [49]. Generally, it is difficult to achieve site- and stereoselective control over radical reactions. The radical species are very reactive and a complex

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

• which will react further. However, reactions catalyzed by the Lewis-acidic character of iron salts are beyond the scope of this review. Iron also has the ability to transfer one or two electrons to a substrate. This opens the possibility for radical reactions via a single electron transfer (SET). Once

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• tend to recombine and eventually generate benzylcobalamin in a parasite pathway. However, the presence of Ti(III) citrate reduces the Co(II) radical, thereby overcoming the “persistent radical effect” observed in cobalt-mediated radical reactions and allowing benzylic radical dimerization to afford 33

Free-radical cyclization approach to polyheterocycles containing pyrrole and pyridine rings

• Ivan P. Mosiagin,
• Olesya A. Tomashenko,
• Dar’ya V. Spiridonova,
• Mikhail S. Novikov,
• Sergey P. Tunik and
• Alexander F. Khlebnikov

Beilstein J. Org. Chem. 2021, 17, 1490–1498, doi:10.3762/bjoc.17.105

• competitive radical reactions. Methyl and methoxy substituents in the 2-phenyl ring (Table 2, entries 5–9) did not affect the cyclization, whereas the presence of 3- or 4-NO2-substituents (Table 2, entries 10 and 11) led to tarring of the reaction mixtures probably due to participation of the NO2 group in

• side radical reactions. The fact that this result is not related to the electron-withdrawing nature of this substituent follows from the fact that another strong EWG at the position 4, such as cyano, did not interfere with the reaction, and the product was obtained in good yield. (Table 2, entry 12

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• -metal catalysts, such as in the Suzuki–Miyaura and Heck coupling reactions. Methodologies for forming different C–C bonds have recently been developed in the field of single-electron chemistry [63][64][65]. Considering that EDA-complex-initiated free-radical reactions are carried out under mild

Helicene synthesis by Brønsted acid-catalyzed cycloaromatization in HFIP [(CF₃)₂CHOH]

• Takeshi Fujita,
• Noriaki Shoji,
• Nao Yoshikawa and
• Junji Ichikawa

Beilstein J. Org. Chem. 2021, 17, 396–403, doi:10.3762/bjoc.17.35

• reactions (Scheme 1a). Diels–Alder (Scheme 1b) [15] and radical reactions (Scheme 1c) [16] directed toward helicene synthesis require high temperature conditions even for low to moderate yields. Olefin metathesis (Scheme 1d) [17] and alkyne trimerization (Scheme 1e) [18][19] require the use of expensive

A novel and robust heterogeneous Cu catalyst using modified lignosulfonate as support for the synthesis of nitrogen-containing heterocycles

• Bingbing Lai,
• Meng Ye,
• Ping Liu,
• Minghao Li,
• Rongxian Bai and
• Yanlong Gu

Beilstein J. Org. Chem. 2020, 16, 2888–2902, doi:10.3762/bjoc.16.238

• , ring-closing, metathesis, cycloadditions, radical reactions and microwave-assisted reactions [38][39][40]. In this work, we attempt to develop a greener, simpler, more efficient and recyclable system to synthesize arylpyridine derivatives. Initially, the reaction of acetophenone (5a) and 1,3