Dodging the Conventional Reactivity of o -Alkynylanilines under Gold Catalysis for Distal 7- endo - dig Cyclization.

A direct ring-closing strategy involving a less facile 7- endo - dig carbacyclization of o -alkynylaniline derivatives for the synthesis of benzo[ b ]azepines has been presented. The trivial well-documented 5- endo-dig cyclization in o -alkynylaniline derivatives due to high nucleophilicity of nitrogen has been overcome by using their vinylogous amides under gold catalysis to access a wide array of benzo[ b ]azepines in an atom economical way with excellent functional group compatibility. Deuterium scrambling experiments and DFT studies favor a mechanism involving stabilizing conformational change of the initially formed seven-membered vinyl gold intermediate through a key cyclopropyl gold carbene intermediate and its subsequent protodeauration mediated by the counter anion.