Oxidation 2-substituierter Pyrrolidine und Piperidine als Nicotinanaloga / Oxidation of 2-substituted Pyrrolidines and Piperidines as Nicotine Analogues

Abstract

The oxidation of nicotine (1) with Hg(II)-EDTA follows the direction to the α-methylene group of the pyrrolidine part and results in a two-step dehydrogenation to lactam 3. The same course is observed with the aromatic or heteroaromatic 2-substituted compounds 4 - 7 to give the pyrrolidones 8 - 11. In contrast, the 2-methyl- or 2-methylaryl-substituted pyrrolidines 12 - 14 are attacked at the α-methine group with only a two-electron withdrawal and give rise to the iminium derivatives 15 - 17. These salts as well as the corresponding enamines show, after addition of D2O, exchange phenomena in the NMR spectra, which indicate an equilibrium in each case. The Hg(II)-EDTA dehydrogenation in the homologous piperidine series gives the corresponding results. From the anabasine derivative 18 the lactam 19 is produced, and from 2-benzyl-1-methylpiperidine (21) the iminium compound 22 is obtained.