Stereoretentive\nDecarboxylative Amidation of α,β-Unsaturated\nCarboxylic Acids to Access Enamides

Enamides have emerged as robust alternatives for enamines,\nexhibiting\nversatile reactivity for further synthetic modifications, including\nnucleophilic addition, cycloaddition, and asymmetric hydrogenation.\nWhile transition-metal-catalyzed cross-coupling of alkenyl (pseudo)halides\nwith amides has been widely employed to construct this valuable scaffold,\nit suffers from some limitations, such as the need for transition-metal\ncatalysts and the preparative synthesis of alkenyl (pseudo)halides.\nIn this study, we report a mild and convenient stereoretentive decarboxylative\namidation of α,β-unsaturated carboxylic acids with easily\nprocurable 1,4,2-dioxazol-5-ones, providing a practical synthetic\nroute to enamides. Density functional theory (DFT) calculations revealed\na plausible reaction mechanism, which involves the nucleophilic addition\nof a carboxylate onto dioxazolone, followed by sequential concerted\nrearrangements.