Highly Selective Synergistic Copper(I/II)‐Catalyzed A 3 Cross Coupling/Decarboxylative A 3 Domino Reactions in Water

A microwave‐assisted copper‐catalyzed A 3 cross‐coupling/decarboxylative A 3 domino reaction of a propiolic acid, an aldehyde, a formaldehyde solution and an amine is described. This strategy represents the first one‐pot cross‐coupling reaction for the direct synthesis of trisubstituted unsymmetrical 2‐butynes with a broad functional group tolerance in good yields (up to 91 %) and excellent chemoselectivity. The simultaneous activation of both the C−COOH and C−H bond of propiolic acid is crucial in this approach, and only carbon dioxide and water are generated as byproducts.