Palladium-Catalyzed Amination of Aryl Bromides Utilizing Arene−Chromium Complexes as Ligands

The arene−chromium complexes of o-diphenylphosphino α-phenylethylamine or α-phenylethyl methyl ether derivatives were examined with regard to their activity as ligands for palladium(0)-catalyzed aryl amination of aryl bromides with a variety of amines. Both steric and electronic factors were found to be significant for the efficient palladium-catalyzed aryl amination reactions. Modulation of the inductive capacity of the arylphosphine atom was achieved by photoinduced ligand exchange of one carbonyl of the chromium tripode in the presence of electron-donating triphenylphosphine or phosphite. Among these arene−chromium ligands, the use of the monophosphine- or monophosphite-(dicarbonyl)chromium of N,N-dimethyl α-(o-diphenylphosphino)phenylethylamine and methyl α-(o-diphenylphosphino)phenylethyl ether produced the palladium(0)-catalyzed aryl amination products with cyclic amines or acyclic secondary amines in high yields; the corresponding strong electron-withdrawing tricarbonylchromium complex resulted in a modest yield of the aryl amination.