Metal-free photoredox-catalyzed direct α-oxygenation of ,-dibenzylanilines to imides under visible light.

An efficient synthesis of imides using metal-free photoredox-catalyzed direct α-oxygenation of ,'-disubstituted anilines in the presence of 9-mesityl-10-methylacridinium [Acr-Mes]BF as a photoredox catalyst and molecular oxygen as a green oxidant under visible light was developed. This photochemical approach offered operational simplicity, high atom economy with a low E-factor, and functional group tolerance under mild reaction conditions. Control and quenching experiments confirmed the occurrence of a radical pathway and superoxide radical anion α-oxygenation reactions, and also provided strong evidence for the reductive quenching of [Acr-Mes]BF based on a Stern-Volmer plot, which led to the proposed mechanism of this reaction.