Controlling chemoselectivity in copper-catalyzed decarboxylative A3/A3 cross-couplings: direct formation of unsymmetrical 1,4-diamino-2-butynes

A direct cross-coupling of propiolic acid with two kinds of in situ formed iminiums has been achieved via the CuI/CuCl2-catalyzed decarboxylative A(3)/A(3) domino process. This novel protocol to synthesise unsymmetrical 1,4-diamino-2-butynes is operationally simple in an atom-and step-economical manner, and provides products in moderate to excellent yields with high chemoselectivity.