Chiral Propargylamines: 4-Piperidinone as Protecting Group

Significance

The preparation of primary propargylamines through multicomponent reactions with aldehydes generally employ N,N-dibenzyl­amines or N,N -diallylamines. However, the selective cleavage of the dibenzyl groups is difficult in the presence of the alkyne, and the more easily cleaved diallyl groups suffer from low ee in the coupling reaction. The reported sequence illustrates that 4-piperidone can be used as a syn­thetic ammonia equivalent. A variety of aldehydes participate in the reaction, affording propargylic amines in synthetically useful yields and good to excellent ee values. Deprotection was accomplished using a solid-support scavenger to immobilize the piperidone and yielded the free propargylic amines in high yields.