Cascade synthesis of indolizines and pyrrolo[1,2-]pyrazines from 2-formyl-1-propargylpyrroles.

A straightforward synthesis of indolizines and pyrrolo[1,2-]pyrazines was performed through a cascade condensation/cyclization/aromatization reaction of substituted 2-formyl--propargylpyrroles with active methylene compounds such as nitromethane, alkyl malonates, methyl cyanoacetate and malononitrile. Under basic conditions, the reaction proceeded satisfactorily to provide the corresponding 6,7-disubstituted indolizines. The condensation of the pyrrolic analogues with ammonium acetate gave rise to pyrrolo[1,2-]pyrazines in high yields.