Photoredox-Mediated Aerobic Oxidative Cleavage of 1,3-Diketones to Access 1,2-Diketones and (Z)-1,4-Enediones

An aerobic oxidative cleavage of 1,3-diketones under visible light irradiation using an organic dye as a photocatalyst is disclosed. The newly developed reaction provides practical access to 1,2-diketones and (Z)-1,4-enediones in moderate to good yields with absolute regio- and stereoselectivity. Mechanistic studies of the reaction suggest that tetraketone intermediates might undergo a photocatalytic energy transfer from the excited photocatalyst to form biradical-like (n,π*) states of ketones.

Bidirectional Elongation Strategy Using Ambiphilic Radical Linchpin for Modular Access to 1,4-Dicarbonyls via Sequential Photocatalysis

Organic molecules that can be connected to multiple substrates by sequential C-C bond formations can be utilized as linchpins in multicomponent processes. While they are useful for rapidly increasing molecular complexity, most of the reported linchpin coupling methods rely on the use of organometallic species as strong carbon nucleophiles to form C-C bonds, which narrows the functional group compatibility. Here, we describe a metal-free, radical-mediated coupling approach using a formyl-stabilized phosphonium ylide as a multifunctional linchpin under visible-light photoredox conditions. The present method uses the ambiphilic character of the phosphonium ylide, which serves as both a nucleophilic and an electrophilic carbon-centered radical source. The stepwise and controllable generation of these radical intermediates allows sequential photocatalysis involving two mechanistically distinct radical additions, both of which are initiated by the same photocatalyst in one pot with high functional group tolerance. The methodology enables a bidirectional assembly of the linchpin with two electronically differentiated alkene fragments and thus offers rapid and modular access to 1,4-dicarbonyl compounds as versatile synthetic intermediates.

Squaraines as near-infrared photocatalysts for organic reactions

Herein, unprecedented uses of squaraine derivatives as new organic near-infrared photocatalysts are reported. These efficient molecular tools are able to promote oxidation and reduction for organic transformations through photocatalytic conditions. A mechanistic investigation is performed to distinguish between competitive Single Electron Transfer and Energy Transfer pathways.

Charge Transfer Complex Enabled Photoreduction of Wittig Phosphonium Salts

A photoinduced charge transfer complex strategy enabled (alkoxycarbonyl)methylation reaction of alkenes with phosphonium salts has been reported. This strategy provides a convenient strategy to functionalize indoles, 1,1-diphenylethylenes, enamides and N-phenyl...

Visible-light enabled photochemical reduction of 1,2-dicarbonyl compounds by Hünig's base

A visible-light enabled, chemoselective photoreduction of 1,2-dicarbonyl compounds by using Hünig's base as reductant is reported.