Conformation of the piperidine ring in isomeric 1,2,5-trimethyl-4-phenyl(triorganosilyl)piperidin-4-ols from the PMR spectra

A full analysis of the PMR spectra of isomeric promedol alcohols was undertaken for the first time. It was shown that the conformational equilibrium must be taken into account only in the case of the Β isomer, where it is determined mainly by chair-chair interconversion. In the α isomers of 1,2,5-trimethyl-4-triorganosilylpiperidin-4-ols an equilibrium was found between the chair conformation and the two skew boat conformations, which are stabilized by an intramolecular hydrogen bond and by the large size of the triorganosilyl substituent. © 1987 Plenum Publishing Corporation