A Novel Strategy for the Synthesis of 3-(N-Heteryl)pyrrole Derivatives

A flexible approach to unknown 1-(1H-pyrrol-3-yl)pyridinium salts with selective control of the substitution patterns, by the reaction of pyridinium ylides with 2H-azirines, is disclosed. 3-(Pyridinium-1-yl)pyrrolides, a new type of stable ylide, were prepared from these salts in high yields by treatment with base. Atmospheric-pressure hydrogenation of the ylides with Adams' catalyst lead to 1-(pyrrol-3-yl)piperidines in good yields.