Regioselective Synthesis of 3-Benzazepinones and Unexpected 5-Bromo-3-benzazepinones

A regioselective hydroamidation of 2-(1-alkynyl)phenylacetamides with Au(PPh3)Cl/AgSbF6 as the catalyst proceeded by a 7-endo-dig pathway to afford 3-benzazepinones. This method accommodates a broad range of alkyl and aryl alkynyl substitutes in moderate to high yields (63-91%). Moreover, unexpectedly, we also discovered a gold-mediated transformation from 2-(1-alkynyl)phenylacetamides to 5-bromo-3-benzazepinones, and AuBr3 was found to not only play an activation role but also act as a reactant in the reaction for the first time.