Use of a Semihollow‐Shaped Triethynylphosphane Ligand for Efficient Formation of Six‐ and Seven‐Membered Ring Ethers through Gold(I)‐Catalyzed Cyclization of Hydroxy‐Tethered Propargylic Esters

The formation of six‐ and seven‐membered ring ethers from hydroxy‐tethered propargylic esters was efficiently catalyzed by a cationic gold(I) complex with a semihollow‐shaped triethynylphosphane ligand. This gold catalysis showed a tolerance toward the reactions of primary, secondary, and tertiary alcohol substrates with various substitution patterns. A sterically congested 2,2,6,6‐tetraalkyl‐substituted tetrahydropyran derivative as well as 6,6‐ and 7,6‐fused bicyclic diethers were obtained in useful yields. In addition, the gold catalysis was applicable to the reaction of a sulfonamide‐tethered propargylic ester to give a piperidine derivative.