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 (B(2)pin(2)) 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.