Gold-Catalyzed Carbocyclization of Phenols with a Terminal Alkyne via an Intramolecular ipso-Friedel-Crafts Alkenylation

We have developed a novel synthetic method to furnish spiro[4.5]cyclohexadienones using an gold-catalyzed carbocyclization of phenols with a terminal alkyne via an intramolecular ipso-Friedel-Crafts alkenylation. Using 2-5 mol% of gold catalyst, 1 equiv. of methanesulfonic acid, and 1 equiv. of 2,6-di-tert-butylpyridine, a variety of spiro[4.5]cyclohexadienone derivatives with an exocyclic olefin unit was obtained in good to excellent yields. The divergent synthesis of dihydronaphthalene derivatives was also examined based on the newly developed gold catalysis.