Chemoselective Chan-Lam coupling by directly using copper powders via mechanochemical metal activation for catalysis

A highly chemoselective Chan-Lam coupling of (benz)imidazoles, anilines and alkyl amines has been developed by directly using catalytic amount of commercial copper powders in methanol via mechanochemical metal activation for catalysis capable of integrating metal surface activation, catalyst formation and catalysis. Fine electronic effects of NH counterpart, coordination requirement from arylboronic acids and unique performance of co-catalyst actetates on suppression of oxidation decomposition of air-labile anilines have been observed, indicating different chemistry under the mechanochemical metal activation for catalysis from that in conventional solution systems. A modified copper(I-II-III) catalytic cycle involving peroxocopper(II) intermediates has been proposed to explain the observed chemistry, in which mono(amido)copper(I) and bis(amido)copper(II) intermediates represent the catalytically active and low or inactive species, respectively, depending on the NH substrates.