AuCl-Catalyzed [4+2] Benzannulation between o-Alkynyl(oxo)benzene and Benzyne

[Structure: see text] The AuCl-catalyzed benzannulation of o-alkynyl(oxo)benzenes with benzenediazonium 2-carboxylate proceeds under mild conditions and a variety of anthracene derivatives, having a ketone group at the 9-position, are produced in good to high yields. The reaction proceeds most probably through the [4+2] cycloaddition between benzyne and benzopyrylium auric ate complex, which would be generated by the gold-induced electrophilic cyclization of o-alkynyl(oxo)benzenes.