Organobismuth Compounds as Aryl Radical Precursors via Light-Driven Single-Electron Transfer

A light-driven method for the generation of aryl radicals from triarylbismuth(III) and (V) reagents is described. Aryl radical generation is proposed to occur through ligand-assisted mesolytic cleavage of an organobismuth(IV) intermediate generated from either oxidation of Bi^III or reduction of Bi^V. This mode of aryl radical generation is demonstrated to be compatible with a range of bimolecular radical arylations, including hydroarylation of electron-deficient olefins and arylation of diboronates, disulfides, sulfonyl cyanides, phosphites and isocyanides. The intermediacy of an aryl radical is supported by radical trapping and radical clock experiments, and Bi^IV-aryl mesolysis is supported computationally.