Photoinduced Three-Component Difluoroamidosulfonylation/Bicyclization: A Route to Dihydrobenzofuran Derivatives

Photocatalytic Bicyclization of Indole-Tethered 1,6-Enynes for Diastereoselective Synthesis of Pyrrolo[3,2,1-jk]carbazoles

A visible-light-driven photocatalytic protocol is established for the diastereoselective synthesis of pyrrolo[3,2,1-jk]carbazoles via a radical-triggered multicomponent bicyclization reaction starting from readily available indole-tethered 1,6-enynes and α-benzyl-α-bromomalonates under mild conditions. This photocatalytic approach exhibits a wide substrate compatibility and excellent tolerability toward various functional groups and boasts the benefit of efficient ring formation and chemical bond creation.

Sustainable Synthesis through Catalyst-Free Photoinduced Cascaded Bond Formation

The beginning of photochemical reactions revolutionized synthetic chemistry through sustainable practices. This review explores cutting-edge developments in leveraging light-induced processes for generating cascaded C-C and C-hetero bonds without catalysts. Significantly, catalyst-free photoinduced methodologies have garnered considerable attention, especially in the creation of varied heterocyclic frameworks for drug design and the synthesis of natural products. The article delves into underlying mechanisms, addresses limitations, and evaluates various methodologies, emphasizing the potential of photocatalyst and transition metal-free photochemical reactions to enhance sustainability. Divided into two sections, it covers recent strides in C-C and C-heteroatom and multiple C-heteroatom bond formation reactions.

Et2Zn-Mediated Radical (3 + 2) Cycloaddition of Vinyl Azides with Ethyl Iododifluoroacetate to Access 3,3-Difluoro-γ-lactams

A diethylzinc-mediated radical (3 + 2) cycloaddition of vinyl azides with ethyl iododifluoroacetate is presented. The developed reaction features good functional group tolerance, broad substrate scope, and operational simplicity, enabling efficient assembly of a wide range of 3,3-difluoro-γ-lactam derivatives bearing an O-substituted quaternary carbon center in moderate to good yields. The utility of the method is showcased by a scaled-up reaction, conversion of the product, and late-stage structural modifications of a variety of pharmaceutical compounds.

Visible light driven multicomponent synthesis of difluoroamidosulfonyl quinoline derivatives

A visible-light-induced photocatalyst-free three-component radical tandem cyclization of N-propargylamine and N-allylbromodifluoroacetamides with the insertion of sulfur dioxide has been developed. Diverse difluoroamidosulfonylated quinolines are obtained in moderate to good yields. This protocol features broad functional group tolerance and high regioselectivity. Moreover, mechanistic studies reveal the involvement of the radical pathway and the formation of an electron donor-acceptor (EDA) complex in this reaction.

Phototriggered Self-Catalyzed Three-Component Minisci Reaction: A Route to β-C(sp3) Heteroarylated Alcohols/Ethers

Herein, a visible-light-triggered photocatalyst-free radical cascade Minisci reaction of heteroarenes, alkenes, and water/alcohols to obtain diverse β-C(sp³) heteroarylated alcohols/ethers has been developed. Achieved under mild and simple conditions, this protocol is scalable and features broad substrate scope and functional group tolerance. Mechanistic studies demonstrate that the heteroarene can be served as a photocatalyst to engage single-electron transfer with persulfate.

Visible-Light-Catalyzed Tandem Radical Addition/1,5-Hydrogen Atom Transfer/Cyclization of 2-Alkynylarylethers with Sulfonyl Chlorides

A novel visible-light-catalyzed tandem radical addition/1,5-hydrogen atom transfer/cyclization cascade of 2-alkynylarylethers with sulfonyl chlorides in 2-methyltetrahydrofuran was developed under photocatalyst- and additive-free conditions. This reaction relies on unique energy transfer and solvent-radical relay strategies to generate sulfonyl radicals for the preparation of a series of sulfonyl-functionalized dihydrobenzofurans in moderate to high yields catalyzed by visible light or solar radiation.