Enantioselective Oxidative Coupling of Carboxylic Acids to α-Branched Aldehydes.

A new reactivity in organocatalysis is proposed to account for the coupling of carboxylic acids to α-branched aldehydes by combining primary amine catalysis and an oxidant. The developed methodology is an enantioselective α-coupling of aromatic and aliphatic carboxylic acids to α-branched aldehydes and proceeds in high yields (up to 97%) and for most examples good enantioselectivities (up to 92% ee). On the basis of experimental and mechanistic observations, the role of the primary amine catalyst is discussed.