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

• cyanins ideal for a variety of synthetic applications, such as polymerization and radical-mediated reactions, often difficult for catalysts operating under visible light. Cyanin compounds can be categorized based on their structural motifs, such as closed-chain cyanins, streptocyanins, and merocyanins

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

• -catalyzed electrochemical reactions are expected in the near future, developing powerful tools for sustainable and efficient organic syntheses. General mechanisms of traditional and radical-mediated cross-coupling reactions. Types of electrocatalysis (using anodic oxidation). Recent developments 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

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

• group of the iodonium salt was also investigated. A potential radical-mediated mechanism was evaluated. Under mild conditions, a base-promoted arylation of general sulfinates 86 without the need for transition metals was introduced using diaryliodonium salts 16 as an aryl source (Scheme 35). Inspired by

C–H Trifluoromethylthiolation of aldehyde hydrazones

• Victor Levet,
• Balu Ramesh,
• Congyang Wang and
• Tatiana Besset

Beilstein J. Org. Chem. 2024, 20, 2883–2890, doi:10.3762/bjoc.20.242

• various transformations [54][55][56][57][58][59][60][61][62][63][64]. In consequence, a large number of transition-metal-catalyzed or radical-mediated processes for C–H functionalization of aldehyde hydrazones has flourished over the years. An ideal scenario for a direct and sustainable synthetic route

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

Cofactor-independent C–C bond cleavage reactions catalyzed by the AlpJ family of oxygenases in atypical angucycline biosynthesis

• Jinmin Gao,
• Liyuan Li,
• Shijie Shen,
• Guomin Ai,
• Bin Wang,
• Fang Guo,
• Tongjian Yang,
• Hui Han,
• Zhengren Xu,
• Guohui Pan and
• Keqiang Fan

Beilstein J. Org. Chem. 2024, 20, 1198–1206, doi:10.3762/bjoc.20.102

• the potential involvement of a radical-mediated catalytic mechanism in AlpJ-family oxygenases, we investigated the impact of supplementing the reaction mixture of 8 and AlpJ, Flu17, or JadG with SOD. The results revealed that adding 5,000 U/mL SOD quenched the tested reactions, with no discernible

• the stable CM• radical through electron paramagnetic resonance. Based on previous studies of cofactor-independent oxygenases and our results, we propose a radical-mediated catalytic mechanism for the cofactor-independent AlpJ-family oxygenases (Scheme 2). The catalytic cascade was initiated by

• formation of product 4, which through a presumed radical-mediated reaction could spontaneously convert to the dimer 5. Additionally, compound 12 had the potential to be oxidized to hydroquinone–kinobscurinone 10, a proposed precursor of kinobscurinone. When employing 1 as the substrate, such cofactor

Palladium-catalyzed three-component radical-polar crossover carboamination of 1,3-dienes or allenes with diazo esters and amines

• Geng-Xin Liu,
• Xiao-Ting Jie,
• Ge-Jun Niu,
• Li-Sheng Yang,
• Xing-Lin Li,
• Jian Luo and
• Wen-Hao Hu

Beilstein J. Org. Chem. 2024, 20, 661–671, doi:10.3762/bjoc.20.59

• electrophilic trapping of onium ylides generated from metal carbenes with nucleophiles, providing an ingenious difunctionalization strategy for diazo compounds to access structurally complex and diverse molecules (Scheme 1b, top) [28][29]. In recent years, radical-mediated MCRs with diazo compounds have become

• a highly emerging area of research and exhibit complementary reactivity to those well-developed carbene-mediated MCRs [30][31][32][33][34][35][36][37][38][39][40][41][42]. In the radical-mediated difunctionalization of alkenes, the carbon-centered radical species from a diazo compound can add to

• limitation of the photoinduced palladium-catalyzed carboamination reactions and the radical-mediated difunctionalization of alkenes with diazo compounds. We envisioned an interesting MCR strategy with mild conditions to access unsaturated γ- and ε-AA derivatives via a π-allyl Pd radical-polar crossover

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

• photocatalytic radical-mediated dearomatization, with H2O serving as the nucleophile [54] (Scheme 9A). Despite the presence of H2O in the reaction, the reduction of 38 to its corresponding radical anion 39 could occur without the need for hydrogen-bonding (Scheme 9B). Cyclic voltammetry measurements of NHPI

• example, the NHPI ester derived from pivalic acid 58 and Hantzsch ester HE form EDA complex 59 which participates in radical mediated hydroalkylation reactions [60][61] (Scheme 13A). In the presence of electron deficient olefin 60, classic Giese-type addition takes place under photocatalyst-free

• form product 132 or by the in-situ-generated tetrachlorophthalimyl anion (–TCPhth) affording product 105. Stoichiometric reductants can facilitate certain radical-mediated transformations that involve NHPI esters, even without the presence of metal catalysts. Larionov and Sun have independently

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

• electron-deficient position of the pyridine ring in complex B to obtain pyridine radical C, which aromatizes through tert-butoxyl radical-mediated extraction of hydrogen to afford the desired 2-substituted pyridine and regenerate Sc(OTf)3. In 2019, Liu et al. first reported an enantioselective CDC of

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

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

• a TEMPO-trapped adduct (4) was detected by HRMS (Scheme 4a). Moreover, the radical-mediated ring-opening product 3am could be obtained with 66% yield in a radical clock experiment when redox-active ester 5 was engaged to react with acrylamide 1a under standard conditions (Scheme 4b). Finally, it

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• [98][99][100]. Preliminary biological screening indicates that members of this class are able to overcome multidrug resistance in vincristine resistant cells [98][99][100]. To access the common scaffold 188, the group relied on an intramolecular gold-photocatalyzed radical-mediated cyclization of an α

• meroterpenoids (Lou). Divergent synthesis of crinipellins by radical-mediated Dowd–Backwith rearrangement (Xie and Ding). Divergent total synthesis of Galbulimima alkaloids (Shenvi). Divergent synthesis of eburnane alkaloids (Qin). Divergent synthesis of Aspidosperma alkaloids (Boger). Photoredox based synthesis

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

• amine nucleophiles [139]. Following an iminyl radical-mediated intramolecular 1,5-cyclization, the subsequent alkyl radical could propagate across carbon monoxide, eventually terminating with an alkyl or aryl amine. In the following year, the Li group described an interesting radical cyclization of β,γ

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

• cycle involving the generation of methyl radicals via β-scission of a tertiary radical which in turn was generated from trimethyl orthoformate by a photogenerated chlorine radical-mediated HAT process (Figure 14) [92]. Recently, Stahl devised a photoredox nickel-catalyzed methylation of benzylic and α

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• “Guareschi 1897 reaction”, is one of the most unusual reactions in organic chemistry, involving the radical-mediated paradoxical aerobic generation of hydrocarbons in near-neutral water solution. A discussion of the mechanism of this amazing reaction, the only metal-free process that generates hydrocarbons

• so-called “1897 reaction” is not well known [7], despite that the unique mechanistic aspects make it one of the most unusual reactions in organic chemistry, involving the paradoxical radical-mediated aerobic generation of hydrocarbons in water under only slightly basic conditions [8]. Also

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

• Nazarov cyclization with the strong silylating agent Me3Si+ B(OTf)4− to afford the corresponding 2-fluorocyclopentenone derivatives, e.g., compound 124 (Scheme 54) [37][90]. Radical-mediated ring-opening reaction: The photochemical iodine atom-transfer ring opening of 1,1-difluoro-2-(1-iodoalkyl

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• ) catalyst and subsequent base-promoted epimerization produced meloscine (158) in 83% yield. In 2017, Yang and co-workers disclosed the synthesis of (−)-pavidolide B (166) by using a thiyl-radical-mediated [3 + 2] annulation reaction to create four contiguous stereocenters on tricycle 162 in one step [71][72

• -cation equivalent in [3 + 2] cycloaddition in the synthesis of (±)-cuparene (13) [69]. The recent advances of [3 + 2] annulation in natural product synthesis. (A) The preparation of meloscine (158) features a cascade radical annulation of divinylcyclopropane [70]. (B) Thiyl-radical-mediated [3 + 2

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

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

• alkanes provided an efficient protocol for the synthesis of alkanes from carboxylic acid substrates previously inaccessible through other methods. The mechanism of this reaction is similar to the previously proposed mechanism in Scheme 19. Isomerization reactions Thiyl radical-mediated isomerizations of C

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• heteroarylated to give the desired dehalogenated products 13.3 or arylheteroarenes 13.4. Other organic dyes, such as dicyanoanthracene (OD5) and rhodamine 6G (OD14), have been successfully used in similar conPET strategies for the aryl radical-mediated derivatization of aryl bromides [82][83]. A similar double

• acceptors 18.2 to afford the desired ketone 18.3. Recently, the Melchiorre group reported a carbamoyl radical-mediated metallaphotoredox synthesis of arylamides (Scheme 19) [91]. In this protocol, excited-state 4CzIPN (OD6) oxidizes a 4-carbamoyl-1,4-dihydropyridine 19.1, which then fragments, releasing the

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• ]. Benzaldehyde (8) was tested as an alternative to tertiary amines, which are commonly employed in radical-mediated reactions due to their ability to bind to atmospheric oxygen, which inhibits such reactions. The quinoxalines 32 were used as the prime photoinitiators, and the reaction was placed in a

Room-temperature Pd/Ag direct arylation enabled by a radical pathway

• Amy L. Mayhugh and
• Christine K. Luscombe

Beilstein J. Org. Chem. 2020, 16, 384–390, doi:10.3762/bjoc.16.36

• -temperature, Pd/Ag-catalyzed direct arylation systems are radical-mediated. This is in contrast to the commonly proposed two-electron mechanisms for direct arylation and appears to extend to other substrates such as benzo[b]thiophene and pentafluorobenzene. Keywords: direct arylation; indole; palladium

• studies are needed to conclusively indicate a radical mechanism, the trap experiments and room-temperature reactivity indicate that a radical-mediated mechanism similar to the indole direct arylation may be governing the observed reactivity. Conclusion In conclusion, in the midst of investigating room

• iodobenzene. Moreover, other substrates such as benzo[b]thiophene and pentafluorobenzene appear to undergo a radical-mediated Pd/Ag room-temperature direct arylation. This is a useful insight for advancing the direct arylation knowledge base, and serves as inspiration for designing new polymerization systems

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• 2011, Nagib and MacMillan reported the synthesis of a broad scope of trifluoromethylated products via a radical-mediated methodology using photoredox catalyst 13 (Scheme 13) [113]. In comparison to other reported methods that used harsher reaction conditions, they carried out the reaction using

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264