Oxime derivatives of 1,2,5-trimethylpiperidin-4-one, 2-methyl-, and 2-(2-furyl)-4- ketodecahydroquinoline react with acetylene to form substituted pyrrolo(3,2-c)piperidines and their N-vinyl derivatives. During the course of pyrrolization the configuration at the 7-position is partially changed, resulting in the formation of two stereoisomeric pyrroles.

The application or utilization of substituted piperidin-4-one oximes I and their bicyclic derivatives, decahydroquinolin-4-ones II-V, in pyrrole synthesis reactions [1] is a promising area of research, both for the search for new physiologically active substances as well as for studying the stereochemical aspects of the reaction, which have remained unexplored until now. Both of these factors underlie the purpose of the present paper. Since the pyrro!ization of 1,2,5-trimethylpiperidin-4-one oxime (I) with acetylene has been studied previously [2, 3], this oxime was used as a model substrate to facilitate the understanding and interpretation of the present results. Reactions of oximes I-V with acetylene were carried out in KOH-DMSO at 85-95~ for 3-7 h (Table 1). R 2 R 1 R 1