Three‐Component Coupling of Aldehydes, Amines, and Alkynes Catalyzed by Oxidized Copper Nanoparticles on Titania

Copper nanoparticles (mainly as Cu 2 O) on titania have been shown to catalyze the multicomponent synthesis of propargylamines from aldehydes, amines, and alkynes (A 3 coupling) effectively at 70 °C under solvent‐free conditions. Both aromatic and aliphatic aldehydes and alkynes have been combined with secondary amines to provide a wide range of propargylamines in moderate to excellent yields. Two examples of ketone/amine/alkyne (KA 2 ) coupling are also included. The catalyst is easy to prepare, reusable at a low copper loading (0.5 mol‐%), and exhibits higher catalytic activity than some commercially available copper sources. Some mechanistic aspects of the reaction have also been examined, which have unveiled the participation of copper(I) acetylides in a heterogeneous process.