Highly Enantioselective Access to Primary Propargylamines:  4-Piperidinone as a Convenient Protecting Group

We report a highly enantioselective, catalytic three-component coupling of aldehydes, alkynes, and 4-piperidone hydrochloride hydrate to afford the corresponding tertiary propargylamines in useful yields. The selective cleavage of the piperidone protecting group using either ammonia/EtOH or a polymer-supported scavenger amine furnishes primary propargylamines.