A Diastereoselective Approach to Enantiopure 3-Substituted Pyrrolidines from Masked Lithium Homoenolates Derived from Norephedrine.

Abstract N-alkoxycarbonyl-2-(2′-bromoethyl)oxazolidines derived from norephedrines are transformed into lithium derivatives by reaction with 1 or 2 equiv of tert-butyllithium in Et2O. The lithium intermediates readily cyclize to bicyclic lactams that react with acetaldehyde and benzaldehyde leading to the addition products in excellent chemical yields and moderate diastereoselectivities. Removal of the chiral appendage provides enantiopure 3-substituted pyrrolidines.