Addition of α-arylmethylidene- or α-alkylidene-β-keto ester enolate to N-activated aldimines via the imino aldol pathway followed by intramolecular aza-Michael reaction in a domino fashion has been developed, and a highly diastereoselective route to substituted piperidines is reported. Enantiopure piperidines are synthesized from chiral sulfinyl imines. Formation and the observed stereoselectivity of the products have been rationalized by mechanistic and computational studies.