Cobalt-Catalyzed Tandem Deamination, Decarboxylation, and Dehomologation of Primary Amines to Carboxylic Acids in Water

Selective transformation of carboxylic acids through oxidative deamination of primary amines is a catalytically challenging and useful transformation. Herein, we present a simple protocol for the transformation of primary amines to carboxylic acids with the readily accessible, cheap cobalt catalyst in the presence of an oxidant, exhibiting good functional group tolerance. While the deamination reaction of benzylamine derivatives proceeds smoothly to provide the corresponding carboxylic acids, the same with substituted 2-arylethylamines under the reaction conditions resulted in the expulsion of carbon dioxide and leads to the formation of the dehomologation product, i.e., carboxylic acids having one carbon atom less. Experimental studies, including control experiments and kinetic studies, were undertaken to shed light on the mechanism.