Abstract 1′-Methylspiro [3H-indole-3, n'-piperidines] 2 can be obtained from the 1-methyl-n- piperidinecarbaldehydes 1 by the Fischer reaction of their phenylhydrazones. The Fischer reaction provides different kinds of products-3H-indole, indole and oxindole-which depend on the N atom position in the piperidine ring.