Visible-Light Photoredox-Catalyzed Synthesis of trans-Oxiranes via Decarboxylative Stereospecific Epoxidation of trans-Cinnamic Acids by Aryldiazonium Salts

Photocatalytic decarboxylation of free carboxylic acids and their functionalization

Visible light mediated decarboxylative functionalization of carboxylic acids and their derivatives has recently emerged as a novel and powerful toolkit for small molecule activation in diverse carbon-carbon and carbon-hetero bond forming reactions. Naturally abundant highly functionalized bench-stable carboxylic acid analogs have been employed as promising alternatives to non-trivial organometallic reagents for mild and eco-benign synthetic transformation with traceless CO2 by-products. In this highlight article, we focus on the development of various photodecarboxylative functionalization strategies along with intra/inter-molecular cyclization via concerted single electron transfer (SET) or energy transfer (ET) pathways. Moreover, widely explored carboxylic acids are systematically classified here into four categories; i.e., α-keto, aliphatic, α,β-unsaturated, and aromatic analogs for a concise overview to the readership. The association of decarboxylative radical species with coupling partners to construct C-C and C-N/O/S/P/X bonds for each analogous acid has been presented in brief.

The efficient synthesis of three-membered rings via photo- and electrochemical strategies

Three-membered rings, such as epoxides, aziridines, oxaziridines, cyclopropenes, vinyloxaziridines, and azirines, are recognized as crucial pharmacophores and building blocks in organic chemistry and drug discovery. Despite the significant advances in the synthesis of these rings through photo/electrochemical methods over the past decade, there has currently been no focused discussion and updated overviews on this topic. Therefore, we presented this review article on the efficient synthesis of three-membered rings using photo- and electrochemical strategies, covering the literature since 2015. In this study, a conceptual overview and detailed discussions were provided to illustrate the advancement of this field. Moreover, a brief discussion outlines the current challenges and opportunities in synthesizing the three-membered rings using these strategies.

Visible-Light-Induced Synthesis of Vinyl Sulfones via Decarboxylative Sulfonylation of Cinnamic Acids Using Sulfonylazides/p-Toluenesulfonylmethyl Isocyanide/β-Keto Sulfones

An efficient visible-light-induced synthesis of vinyl sulfones has been accomplished via decarboxylative sulfonylation of cinnamic acids using sulfonylazides, p-toluenesulfonylmethyl isocyanide, and β-keto sulfones as sulfonyl source, in the presence of inexpensive organic photocatalysts like rhodamine B and eosin Y. The reaction is facile, straightforward, and endowed with wide substrate scope and functional group tolerability.

Photoredox-Catalyzed 1,4-Peroxidation-Sulfonylation of Enynones: A Three-Component Radical Coupling Approach for the Synthesis of Highly Functionalized Allenes

An Eosin Y-catalyzed visible light-promoted 1,4-peroxidation-sulfonylation of enynones was achieved to give tetrasubstituted allenes. The photoredox catalysis of Eosin Y allowed the concomitant formation of peroxy and sulfonyl radicals, where the preferential peroxy radical addition to the alkene moiety of enynones resulted in the subsequent α-keto radical-sulfonyl radical cross couplings. The developed photoredox catalysis of Eosin Y demonstrates a regioselective 1,4-diradical addition strategy, opening up a new possibility of diradical functionalization of conjugate systems.

Visible-Light-Mediated Synthesis of α-Ketoamides via Oxidative Amination of 2-Bromoacetophenones Using Eosin Y as a Photoredox Catalyst

An oxidative amination of 2-bromoacetophenones has been accomplished to provide α-ketoamides by using photoredox catalysis with air as oxidant. The reactants are readily accessible, and the method is endowed with broad substrate scope and good functional group tolerance. The practicality of the approach is also shown by a gram-scale reaction.

NIS-initiated photo-induced oxidative decarboxylative sulfoximidation of cinnamic acids

N-Iodosuccinimide catalyzed, visible-light-induced oxidative decarboxylative cross-coupling between cinnamic acids and NH-sulfoximines is presented. This strategy results in the formation of α-keto-N-acyl sulfoximines via the construction of two new CO bonds and one C-N bond. The in situ-generated N-iodosulfoximine serves as the light-absorbing species in the absence of any external photosensitizer. The keto carbonyl and amidic carbonyl oxygen in the resulting product originate from dioxygen and water respectively.

Copper- and Visible-Light-Catalyzed Cascade Radical Cyclization of N-Propargylindoles with Cyclic Ethers

An efficient visible-light-assisted, copper-catalyzed tandem radical cyclization of N-propargylindoles with cyclic ethers is established. A series of 2-oxoalkyl-9H-pyrrolo[1,2-a]indol-9-ones with potential biological activities were synthesized in moderate yields by using a dual catalytic system with copper acetate as a transition metal catalyst and eosin Y as a visible light catalyst. The investigation of reaction mechanism shows that it goes through a cascade oxoalkyl radical addition, cyclization, and oxidation process.