Azide–Enolate Cycloaddition‐Rearrangement Enables Direct α‐Amination of Amides and Enelactam Synthesis from Esters**

Abstract

Vinyl azides have undergone a recent renaissance as versatile synthetic reagents, however their reactivity as 1,3-dipoles in (3+2) cycloadditions remains underexplored. Here the synthesis of ene--lactam scaffolds via (3+2) cycloaddition of -substituted vinyl azides with ester enolates is established. Mechanistic investigations, including isolation of reaction intermediates and density functional theory calculations, implicate an unprecedented conjugatetype addition to the exocyclic alkene of an N-vinyl triazolinone intermediate generated in the cycloaddition step. Determination of the reaction scope and application to synthesis of the natural product sargassumlactam is reported.