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

Carlos H. Escalante, Fernando A. Carmona-Hernández, Alberto Hernández-López, Eder I. Martínez-Mora, Francisco Delgado, Joaquín Tamariz

Research output: Contribution to journalArticlepeer-review

Abstract

A straightforward synthesis of indolizines and pyrrolo[1,2-a]pyrazines was performed through a cascade condensation/cyclization/aromatization reaction of substituted 2-formyl-N-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-a]pyrazines in high yields. N-Allenyl-2-formylpyrroles behaved as more reactive substrates than 2-formyl-N-propargylpyrroles, furnishing the expected indolizines in higher yields. Hence, an allenyl-containing intermediate was probably generated as the reactive species in the reaction mechanism of some N-propargyl pyrroles prior to the cyclization reaction.

Original languageEnglish
Pages (from-to)396-409
Number of pages14
JournalOrganic and Biomolecular Chemistry
Volume20
Issue number2
DOIs
StatePublished - 14 Jan 2022

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