Electro-organic reactions. Part 23. Regioselectivity and the stereochemistry of anodic methoxylation of N-acylpiperidines and N-acylmorpholines

Abstract

Anodic methoxylation of conformationally biassed N-acylpiperidines has been shown to give axial substitution due to steric constraints imposed by relatively slow rotation of the planar N-acyl groups. These steric constraints also account for the regioselectivity of the reaction and the axial substitution resulting from nucleophilic displacement of the α-methoxy-function in the presence of aluminium chloride. The N-acyl groups adopt anti- and syn-conformations and their relative proportions are consistent with the steric factors invoked to explain the substitution pattern.