SYNTHESIS OF SUBSTITUTED TETRAHYDROPYRIDINES BY CYCLIZATIONS OF SILICON-CONTAINING IMINIUM IONS

Article abstract of DOI:10.1016/S0040-4020(01)86645-X

Trans-2,6-disubstituted-1,2,5,6-tetrahydropyridines are formed stereoselectively from the cyclization of silicon-containing iminium cations 5 if the nitrogen substituents R¹ is an alkyl group.In contrast, cyclization of the corresponding NH or N-acyl iminium ions occurs in a stereorandom fashion.Nonracemic tetrahydropyridines cannot be prepared in this way, since both iminium ion and N-acyliminium ion intermediates racemize prior to cyclization.