The conformational analysis of saturated heterocycles. Part LXIV. Stereochemical orientation of the ethylation of piperidines
Rates of reaction of a series of 1-alkyl-4-phenylpiperidines with ethyl iodide in methanol and in acetonitrile and the proportions of the isomeric quaternary salts formed are reported. Axial ethylation predominates for all cases studied, but the equatorial:axial product ratios often approach unity, and the stereoselectivity is intermediate between those found for methylation (preference for axial attack) and benzylation (preference for equatorial attack).