Organophotoredox-Catalyzed C(sp²)–H Difluoromethylenephosphonation of Imidazoheterocycles

A mild and efficient method for the direct difluoromethylenephosphonation of imidazopyridines has been developed using rose bengal (RB) as a photoredox catalyst. Bis­(pinacolato)­diboron (B₂pin₂) is found to be a crucial additive in the present reaction. The present methodology is also applicable to other heterocycles like imidazo­[2,1-b]­thiazole, benzo­[d]­imidazo-[2,1-b]­thiazole, and indole. The reaction possibly proceeds through a single electron transfer (SET) process.