A Direct Synthesis of Substituted Exocyclic 1H-pyrrol-3(2H)-ones by Base-Mediated Multicomponent [3+2] Cycloaddition

A one-pot, three-component, base-mediated [3+2] cycloaddition reaction to synthesize 1H-pyrrol-3(2H)-ones from readily available amino acid esters, aldehydes, and terminal alkynes was reported. Isolation of the intermediate and the detailed mechanistic study revealed the course of the reaction. This multi-component reaction proceeds via imine formation followed by the nucleophilic addition of alkyne to form a propargylamine precursor. Base-mediated conversion of propargylamine precursor into 1-azadiene followed by in situ ketene formation leading to [3+2] cycloaddition that ultimately produces unusual 1H-pyrrol-3(2H)-ones.