Stereoselective alkylations in rigid systems.: Effect of remote substituents on π-facial additions to lactam enolates.: Stereoelectronic and steric effects

A series of chiral bicyclic lactams has been studied by both experiment and ab initio molecular orbital calculations. The facial selectivity of the alkylation of their enolates shows a high degree of endo or exo entry, depending upon certain substituents and their positions in the lactams. The suggested reasons for the exo or endo selectivity for alkylation were determined to be purely electronic or purely steric in certain instances. The results of the selectivity study now allow the asymmetric synthesis of various ketones, acids, and pyrrolidines in either enantiomeric form based on the choice of lactam employed.