Visible Light Promoted Metal-Free Sustainable Reduction of α-Alkylidene Oxindoles/Succinimides

Abstract

Visible light promoted chemoselective metal free hydrogenation of activated double bond has been achieved via photoredox catalysis. Eosin Y has proved to be an efficient catalyst for the effective reduction of C−C double bonds of alkylidene oxindoles and succinimides under visible light. Commercially viable DIPEA has been employed as a sacrificial electron donor and it's in-situ generated cationic radical acts as reductant in this transformation. The method proved to be practical as a broad range of substrates containing activated double bond were easily reduced. The method proved to be scalable on a gram quantity and the reduced product has been utilized successfully for the further synthetic application. The systematic and detailed mechanistic studies reveal the oxidative quenching of the photocatalyst by the activated double bond.