Stereoretentive Decarboxylative Amidation of α,β-Unsaturated Carboxylic Acids to Access Enamides

Enamides have emerged as robust alternatives for enamines, exhibiting versatile reactivity for further synthetic modifications, including nucleophilic addition, cycloaddition, and asymmetric hydrogenation. While transition-metal-catalyzed cross-coupling of alkenyl (pseudo)halides with amides has been widely employed to construct this valuable scaffold, it suffers from some limitations, such as the need for transition-metal catalysts and the preparative synthesis of alkenyl (pseudo)halides. In this study, we report a mild and convenient stereoretentive decarboxylative amidation of α,β-unsaturated carboxylic acids with easily procurable 1,4,2-dioxazol-5-ones, providing a practical synthetic route to enamides. Density functional theory (DFT) calculations revealed a plausible reaction mechanism, which involves the nucleophilic addition of a carboxylate onto dioxazolone, followed by sequential concerted rearrangements.