The conformational analysis of saturated heterocycles. Part LII. The stereochemical orientation of the benzylation of piperidines

Abstract

N-Methyl-, N-ethyl-, and N-isopropyl-4-phenylpiperidine have been quaternised in acetonitrile, acetone, benzene, and methanol. The product ratios were measured by n.m.r. spectroscopy. For the first two solvents, rate constants were determined and used to calculate individual rates k_a and k_e for axial and equatorial quaternisation. Most of the reactions proceed predominantly by equatorial attack; the individual variations are analysed in terms of k_a and k_e.