CONFORMATIONAL-ANALYSIS AND CONFIGURATIONAL ASSIGNMENT OF 3-(ALKYLSULFENYL)-N-METHYLPIPERIDINIUM, 3-(ALKYLSULFINYL)-N-METHYLPIPERIDINIUM, AND 3-(ALKYLSULFONYL)-N-METHYLPIPERIDINIUM CHLORIDES

H-1, C-13 NMR, DEPT, and two-dimensional H-1-C-13 heteronuclear correlation spectra of 3-(alkylsulfenyl)-, 3-(alkylsulfinyl)- (its two epimeric sulfoxides), and 3-(alkylsulfonyl)-N-methylpiperidinium chlorides (alkyl = methyl, ethyl, isopropyl) have been recorded and fully interpreted. Magnetic resonance parameters (chemical shifts of H-1 and C-13, and geminal and vicinal coupling constants) of these compounds are described for the first time. Conformational analysis has been carried out on conformations selected by a molecular mechanics force field (MMX). In all compounds there is a single ring conformation, the undistorted chair with N-methyl and SOnR (n = 0, 1, 2; R = Me, Et, Pr(i)) in the equatorial orientation. These conclusions are supported by the observed vicinal coupling constants. Configurational assignment of ring nitrogen and carbon C3 has been carried out from observed vicinal axial-axial coupling constants, and the relative configurations of the diastereomeric sulfoxide pairs have been established from observed C-13 chemical shifts for ring carbons C2 and C4.