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

Abstract A one‐pot, three‐component, base‐mediated [3+2] cycloaddition reaction to synthesize 1 H ‐pyrrol‐3(2 H )‐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 1 H ‐pyrrol‐3(2 H )‐ones.