Light-Mediated Dual Phosphine-/Copper-Catalyzed Atom Transfer Radical Addition Reaction.

The atom transfer radical addition reaction catalyzed by triphenylphosphine and copper(I) halide is described. The reaction proceeds under irradiation with 365 nm light using a light-emitting diode and was performed in regular glassware. The proposed mechanism involves the formation of quaternary phosphonium salt, which undergoes single electron reduction by copper(I) salt via photo-induced electron transfer. The method works well for terminal alkenes and activated organic halides such as esters of bromo- and iodoacetic acid and bromoacetonitrile. gem-Difluorinated styrenes, for which atom transfer reactions are rare, also proved to be good substrates for this phosphine-/copper-catalyzed protocol.