We report here two approaches for the preparation of new N-substituted β-enamino ester piperidines featuring an exocyclic tetrasubstituted double bond, based either on the direct alkylation of piperidine β-enamino esters bearing an exocyclic trisubstituted double bond or on the intramolecular cyclization of linear amino β-keto esters. The target compounds were obtained as unusual (Z)-stereoisomers in high yields. The key role of ammonia as reagent ...
