Vinyl imidates in cycloaddition reactions: a formal synthesis of (+/-)-reserpine.

[reaction: see text] The intramolecular Diels-Alder reaction of N-acylvinylimidates provides an efficient entry into cis-fused perhydroisoquinoline ring systems. This is demonstrated by the preparation of isoquinoline 2, an intermediate, which has been previously transformed to reserpine.