Photocatalytic [3 + 2] Annulation of Diazoketones with Enamides via Triplet Carbene Transfer

A photocatalytic [3 + 2] annulation of diazoketones with enamides provides efficient access to α-amido-substituted dihydrofurans under mild conditions. Energy-transfer-generated electrophilic triplet carbenes undergo polarity-matched addition to electron-rich enamides, favoring [3 + 2] annulation over competing cyclopropanation. The NHAc group further serves as a removable synthetic handle for divergent skeletal editing, enabling formal O-to-S and O-to-N exchange and indole annulation to furnish dihydrothiophene, pyrrole, and carbazole derivatives.