Enantioselective Syntheses of Morpholines and Their Homologues via SN2-Type Ring Opening of Aziridines and Azetidines with Haloalcohols

A highly regio- and stereoselective strategy for the syntheses in high yield and enantioselectivity of a variety of substituted nonracemic morpholines and their homologues is described. The reaction proceeds via an S(N)2-type ring opening of activated aziridines and azetidines by suitable halogenated alcohols in the presence of Lewis acid followed by base-mediated intramolecular ring closure of the resulting haloalkoxy amine.