Azlactone rings: uniting tradition and innovation in synthesis

Abstract

Azlactones, also known as oxazolones, are a class of heterocyclic compounds with significant relevance in the synthesis of non-natural amino acids and their derivatives. Their reactivity stems from the presence of both pro-nucleophilic and electrophilic sites, making them highly versatile and enabling a diversity of transformations. In recent years, numerous synthetic strategies utilizing azlactones as key substrates have been developed, encompassing photochemical reactions, cycloadditions, conjugate additions, and dynamic kinetic resolutions. Particular emphasis has been placed on transition-metal catalysis and organocatalyzed processes, which offer precise control over stereo- and/or regioselectivity. This review offers a comprehensive perspective on recent advances in azlactone chemistry, highlighting key reaction mechanisms and activation modes through a variety of examples.