Gold-Catalyzed Cyclization of Alkyne Alcohols: Regioselective Construction of Functionalized 6,6- and 6,7-Bicyclic Ethers.

We describe an efficient regioselective formation of six-/seven-membered cyclic ethers based on gold-catalyzed intramolecular hydroalkoxylation. Sequential gold-catalyzed cyclization and palladium-catalyzed cross-coupling reactions afforded 6,6-bicyclic ethers, while reversing the reaction sequence (cross-coupling then cyclization) afforded 6,7-bicyclic ethers. This methodology should provide access to a range of functional polycyclic ethers.