A regio- and diastereoselective intramolecular nitrone cycloaddition for practical 3- and 2,3-disubstituted piperidine synthesis from gamma-butyrolactone.

A fast and efficient route for diversity-oriented synthesis of 3- and 2,3-disubstituted piperidines, featuring an intramolecular nitrone cycloaddition with high regio- and diastereoselectivity, was achieved in six steps and 36-66% overall yield from commercially available gamma-butyrolactone or 1,4-butanediol. A new N-alkenyl nitrone enoate was used in this intramolecular nitrone cycloaddition, and the regioselectivity, diastereoselectivity, and reversibility of this cycloaddition were investigated.