Photoexcited Nickel-Catalyzed Carbohalogenation

A nickel/blue light-catalyzed carbohalogenation reaction is reported. A nickel catalyst and an inexpensive phosphine ligand promote the reaction of aryl iodides and aryl bromides with π systems to enable the construction of a library of halogenated heterocyclic scaffolds. Mechanistic studies provide insight regarding fundamental steps of the catalytic cycle, including the reversible C–X bond formation via deuterium labeling and EPR experiments, while preliminary enantioselective results suggest a two-electron migratory insertion.