Abstract
Catalytic hydrogenation of six kinds of N-methylpyridinium iodides gave pairs of geometrical isomers in a certain ratio for each methiodide. ortho-Dimethyl derivatives afforded almost exclusively cis isomers, meta derivatives gave cis isomers predominantly, and para derivative produced almost same amounts of both isomers. N-Methylpiperidines thus produced were quaternized with methyl iodide to N, N-dimethylpiperidinium iodides. The chemical shifts of equatorial and axial N-methyl protons were compared with each other, from which the substituent effects of α methyl groups was deduced. The results from nuclear magnetic resonance study enabled us completely to analyze the configurations and conformations of the hydrogenation products and their quaternary salts.
