Cobalt-Catalyzed Monoselective Ortho-C-H Functionalization of Carboxamides with Organoaluminum Reagent.

A simple triphenylphosphine-ligated cobalt catalyst is reported for the direct ortho-C-H methylation and ethylation of aromatic, heteroaromatic, alkenyl, and even aliphatic carboxamides with inexpensive organoaluminum reagents in the presence of a cheap alkyl chloride as oxidant. This reaction shows monoselectivity in contrast with previously established C-H methylation methodologies.