Palladium-Catalyzed Picolinamide-Directed Benzylic C(sp3)-H Chalcogenation with Diaryl Disulfides and Diphenyl Diselenide

The first palladium-catalyzed direct benzylic C(sp(3))-H chalcogenation with diaryl disulfides and diphenyl diselenide has been established. The coupling reaction proceeds between the thioether radical and palladiumcycle intermediate. Picolinamide serves as an excellent directing group for the C-H activation of benzylic C(sp(3))-H and can be easily removed. The current protocol exhibits a relatively broad substrate scope and high functional group compatibility. A mechanistic study indicates that palladium(IV) intermediate is probably formed during the course of the reaction.