Visible-light-driven NHC and organophotoredox dual catalysis for the synthesis of carbonyl compounds

• Vasudevan Dhayalan

Beilstein J. Org. Chem. 2025, 21, 2584–2603, doi:10.3762/bjoc.21.200

• Vasudevan Dhayalan Department of Chemistry, National Institute of Technology Puducherry, Karaikal-609609, Puducherry, India 10.3762/bjoc.21.200 Abstract Over the past two decades, organocatalyzed visible-light-mediated radical chemistry has significantly influenced modern synthetic organic

• ; NHC; organic photocatalyst; radicals; visible-light; Introduction Over the last ten years, NHC-catalyzed visible-light-promoted radical chemistry has been extensively developed for the cost-effective and practical synthesis of bioactive intermediates, pharmaceuticals, drugs, and natural products [1

• desired polycyclic compounds 35 in a moderate level of enantioselectivity (Scheme 14) [64]. Conclusion In conclusion, over the past two decades, organocatalyzed visible-light-promoted radical chemistry, particularly dual photocatalysis combining N-heterocyclic carbenes (NHCs) with organic photocatalysts

Enantioselective radical chemistry: a bright future ahead

• Anna C. Renner,
• Sagar S. Thorat,
• Hariharaputhiran Subramanian and
• Mukund P. Sibi

Beilstein J. Org. Chem. 2025, 21, 2283–2296, doi:10.3762/bjoc.21.174

• catalysis is discussed initially. This is followed by the recently emerging areas of transition-metal catalysis, photoenzymatic catalysis, and electrochemistry. Perspective Radical generation and reactions Synthetic methods based on free radical chemistry are some of the most efficient and powerful tools

• . Additionally, radical chemistry offers opportunities to achieve transformations that may not proceed via two-electron processes. Radicals can be generated through several different approaches, summarized in Figure 1A. The use of organostannanes to generate carbon-centered radicals was formerly commonplace but

• research on auxiliary-based chiral Lewis acid catalysis inspired Porter, Sibi and others to transpose the concept to radical chemistry. A large number of enantioselective radical reactions that were reported during 1996–2007 were mainly based on chiral Lewis acid-mediated/catalyzed free radical reactions

Multicomponent reactions IV

• Thomas J. J. Müller and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2025, 21, 2082–2084, doi:10.3762/bjoc.21.163

• a strong emphasis on heterocycle synthesis. Beyond traditional condensation-based approaches, mechanistically innovative crossovers – linking metal catalysis with radical chemistry and, more recently, with photo(redox) catalysis – are opening entirely new avenues for MCR development. Finally, seven

Chiral phosphoric acid-catalyzed asymmetric synthesis of helically chiral, planarly chiral and inherently chiral molecules

• Wei Liu and
• Xiaoyu Yang

Beilstein J. Org. Chem. 2025, 21, 1864–1889, doi:10.3762/bjoc.21.145

• enantioselectivity. Overall, with the recent rapid advancements of CPA catalysis, along with the utilization of CPA catalysts in asymmetric radical chemistry, transition metal-catalyzed reactions and photoredox chemistry, we envision that CPA catalysts will continue to play a central role in the future asymmetric

Photocatalysis and photochemistry in organic synthesis

• Timothy Noël and
• Bartholomäus Pieber

Beilstein J. Org. Chem. 2025, 21, 1645–1647, doi:10.3762/bjoc.21.128

• -mediated organic synthesis has also resulted in a renaissance of radical chemistry. Once regarded as “[…] messy, unpredictable, unpromising and essentially mysterious” [39], radical-based methods have become central to modern organic chemistry, spanning applications in the life sciences. The Perspective

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

• both difluoromethylated and aryldifluoromethylated benzimidazoles. Inspired by previous work in radical chemistry, we turned our attention to difluoroacetic acid (CF2HCOOH) and α,α-difluorobenzeneacetic acid (PhCF2COOH), both of which are inexpensive and readily available industrial raw materials. In

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

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

• approaches have also gained widespread attention for their unique advantages in these transformations [4]. Radical chemistry often exhibits complementary reactivity to two-electron pathways and can be performed with high selectivity, atom economy, and functional group tolerance [5]. A well-known radical

Synthesis and reactivity of the di(9-anthryl)methyl radical

• Tomohiko Nishiuchi,
• Kazuma Takahashi,
• Yuta Makihara and
• Takashi Kubo

Beilstein J. Org. Chem. 2024, 20, 2254–2260, doi:10.3762/bjoc.20.193

• the field of radical chemistry. However, reducing the reactivity of radical species can mean losing one of their most attractive properties. Therefore, it is very important to explore aromatic hydrocarbon radicals that are sufficiently stable for handling, yet reactive under specific conditions

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

• cross-coupling and radical chemistry, as well as providing versatile synthetic approaches to pyrazoles. This overview summarizes the most important MCR syntheses of pyrazoles based on ring-forming sequences in a flashlight fashion. Keywords: cycloaddition; cyclocondensation; multicomponent reaction

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

• and acyl radicals and maintaining a high degree of selectivity with respect to the desired outcome are key obstacles to the growth of alkyl and acyl radical chemistry. With this in mind, the emergence of new chemical transformations involving radicals generated via C–O bond cleavage by visible light

Ortho-ester-substituted diaryliodonium salts enabled regioselective arylocyclization of naphthols toward 3,4-benzocoumarins

• Ke Jiang,
• Cheng Pan,
• Limin Wang,
• Hao-Yang Wang and
• Jianwei Han

Beilstein J. Org. Chem. 2024, 20, 841–851, doi:10.3762/bjoc.20.76

• -positions to the ester group were all well-tolerated (Table 3). To gain further insights into the reaction mechanism, we conducted control experiments. Given the utility of diaryliodonium salts in radical chemistry, we introduced 2 equivalents of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) or 2 equivalents

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

• , greatly increasing the molecular complexity of the starting substrate. Using radical chemistry would lead to a regioselective addition of azide radicals to the alkene, forming selectively the most stabilized C-centered radical. A prominent method for the generation of azide radicals relies on hypervalent

• azido-hydration reaction [18]. The homopropargylic azide was obtained in only 28% yield using phenyl vinyl ketone. Based on reported aza-alkynylation reactions [19][20][21][22][23] and modern azidation methods using radical chemistry [17][24][25][26] three approaches could be envisaged. All of them

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

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

• Zixiao Wang Feichen Cui Yang Sui Jiajun Yan School of Physical Science and Technology, ShanghaiTech University, 393 Middle Huaxia Rd., Shanghai, 201210, China 10.3762/bjoc.19.116 Abstract Radical chemistry is one of the most important methods used in modern polymer science and industry. Over the

• past century, new knowledge on radical chemistry has both promoted and been generated from the emergence of polymer synthesis and modification techniques. In this review, we discuss radical chemistry in polymer science from four interconnected aspects. We begin with radical polymerization, the most

• constantly acquire new inspirations from organic chemists. Dialogues on radical chemistry between the two communities will deepen the understanding of the two fields and benefit the humanity. Keywords: crosslinking; polymer surface modification; post-polymerization modification; radical chemistry; radical

C–H bond functionalization: recent discoveries and future directions

• Indranil Chatterjee

Beilstein J. Org. Chem. 2023, 19, 1568–1569, doi:10.3762/bjoc.19.114

• the abstraction of intramolecular hydrogen atoms. Radical chemistry is a viable alternative to the two-electron process, involving C–H bond functionalization in the absence of any ligand and using low-cost redox-active metals (Fe, Cu, Mn, etc.) rather than heavy metals (Rh, Ir, etc.). Although radical

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

• challenging-to-generate “uncontrollable” species prone to side reactions to versatile reactive intermediates enabling construction of myriad C–C and C–X bonds. This maturation of free radical chemistry has been enabled by several advances, including the proliferation of efficient radical generation methods

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

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

• generated by reductive decarboxylation, could add in an 8-endo-trig manner (common in radical chemistry) to the alkene and the resulting radical could be oxidized to the cation by the oxidized form of the photocatalyst to close the photocatalytic cycle, followed by formation of the double bond. Even though

Photocatalytic sequential C–H functionalization expediting acetoxymalonylation of imidazo heterocycles

• Deepak Singh,
• Shyamal Pramanik and
• Soumitra Maity

Beilstein J. Org. Chem. 2023, 19, 666–673, doi:10.3762/bjoc.19.48

• acetylating agent. The developed method is heavy-metal free, as shown by the use of inexpensive PTH, as well as a base-free approach, and involves aerial oxygen to generate exciting derivatives, which may prove to be valuable in the field of radical chemistry research in future. Strategies of C-3

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• -positive and Gram-negative bacteria (Scheme 31B). 4.4 Photocatalyzed oxidative ring expansion: alternative radical chemistry for pleuromutilin scaffold construction Following the advent of photoredox catalysis in ring-opening and ring-expansion chemistry [75], a new route was proposed by Foy and Pronin to

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

• of atom economy and protecting-group-free synthesis dominating the field of total synthesis. In this new era, total synthesis is moving towards natural efficacy by utilizing both the biosynthetic knowledge of divergent synthesis and the latest developments in radical chemistry. This contemporary

• chemical libraries with natural scaffolds for biological screening. The evidenced increase of divergent radical syntheses in the last few years indicates that this approach is here to change the way chemists will practice total synthesis in the future. Evolution of radical chemistry for organic synthesis

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

• bonds and can be applied to radical chemistry. This review discusses copper-catalyzed reactions including alkene and alkyne, organic halide, and alkyl C–H functionalization. 3. Visible-light-mediated copper-catalyzed alkene and alkyne functionalization 3.1 Olefinic C–H functionalization and allylic

A visible-light-induced, metal-free bis-arylation of 2,5-dichlorobenzoquinone

• Pieterjan Winant and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 2315–2320, doi:10.3762/bjoc.17.149

• precursor, potentially leading to both regioisomers and unwanted side products, complicating purification. As a result, accounts of bis-arylation using radical chemistry are scarce and report very low yields [29][30][31][32]. While transition-metal catalysis is a viable strategy, it is often based on

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

• , carbanion, and radical chemistry. Furthermore, gem-difluorocyclopropanes readily go through carbonylation, dehalogenation, and annulation, resulting in various useful materials. 2.1 Thermal rearrangements The substitution of hydrogen with fluorine in cyclopropane leads to a significant weakening of the C–C

• . Further applications of free radical chemistry have developed through the use of radical initiators under comparatively mild conditions to form cyclopropylmethyl radicals, which can readily release their strain by opening to give homoallyl radicals. gem-Difluorocyclopropanes, because of their