Gold or no gold: one-pot synthesis of tetrahydrobenz[b]azepin-4-ones from tertiary N-(but-3-ynyl)anilines.

Depending on the tertiary aniline substrates, an efficient, one-pot synthesis of tetrahydrobenz[b]azepin-4-ones needs either gold catalysts or no catalyst at all. In the reaction, the aniline nitrogen plays a unique role in relaying "O" from m-CPBA to a tethered C-C triple bond, which is inert to the oxidant under the mild reaction conditions.