Photochemical acridone-mediated direct arylation of (hetero)arenes with aryl diazonium salts

A metal-free photochemical C-H direct arylation using acridone as a photoredox catalyst to facilitate the reaction is described. Diazonium salts as precursors for aryl radicals, demonstrated by a fluorescence quenching experiment and free radical trapping experiment, allow the functionalization of (hetero)arenes under mild conditions. A series of valuable substituted biaryl and aryl-heteroaryl compounds were prepared in moderate to good yields via the coupling. Moreover, this methodology is shown to be applicable to scale-up synthesis. We have described a convenient strategy for the preparation of valuable substituted biaryls using acridone as a catalyst under visible light. The scope of the reaction for several aryl diazonium salts and (hetero)arenes was investigated.