Iron(III)-Mediated Nucleophilic Cascade Cyclization of Tertiary Enamides with Diselenides for the Construction of 3-Seleno-2-pyridones

An iron(III)-mediated nucleophilic cascade cyclization of N-propiolyl enamides with various diselenides was developed, which provides an efficient way to construct seleno-heterocycles. A mechanism study shows that the cascade process involves the selective addition of diselenides to the C≡C bond generating a seleniranium ion, followed by an intramolecular nucleophilic attack of enaminic carbon of tertiary enamide. Utilizing this protocol, a variety of 3-seleno-2-pyridones were successfully synthesized featuring good functional group compatibility and simple operation.