The substituted piperidines, N-(piperidin-3-en-4-yl)-N-(1,2-dimethoxycarbonyl-etheno)arylamine and 1-aryl-3,4,5,6-tetramethoxycarbonyl-1,2-dihydrospiro[cyclo-[pyridine-2,4′-piperidine], were synthesized by the condensation of acetylenedicarboxylic ester with an azomethine, obtained from a γ-piperidone. It was found that the amounts of 1:1 and 1:2 addition compounds obtained depends on the ratio of starting reagents. Compounds isomeric at the vinyl group were examined in the case of one of the 1:1 addition compounds. N-(1,2,5-trimethylpiperidin-4-yl)-N-(1,2-dimethoxycarbonyletheno)aniline was prepared by two methods. © 1987 Plenum Publishing Corporation.