Visible-Light-Accelerated Copper(II)-Catalyzed Regio- and Chemoselective Oxo-Azidation of Vinyl Arenes

The visible-light-accelerated oxo-azidation of vinyl arenes with trimethylsilylazide and molecular oxygen as stoichiometric oxidant was achieved. In contrast to photocatalysts based on iridium, ruthenium, or organic dyes, [Cu(dap)(2)]Cl or [Cu(dap)Cl-2] were found to be unique for this transformation, which is attributed to their ability to interact with the substrates through ligand exchange and rebound mechanisms. Cu-II is proposed as the catalytically active species, which upon coordinating azide will undergo light-accelerated homolysis to form Cu-I and azide radicals. This activation principle (Cu-II-XCuI+X-.) opens up new avenues for copper-based photocatalysis.