Stereoselective Gold(I)-Catalyzed Intermolecular Hydroalkoxlation of Alkynes

We report the use of cationic gold complexes [Au­(NHC)­(CH₃CN)]­[BF₄] and [{Au­(NHC)}₂(μ–OH)]­[BF₄] (NHC = N-heterocyclic carbene) as highly active catalysts in the solvent-free hydroalkoxylation of internal alkynes using primary and secondary alcohols. Using this simple protocol, a broad range of (<i>Z</i>)-vinyl ethers were obtained in excellent yields and high stereoselectivities. The methodology allows for the use of catalyst loadings as low as 200 ppm for the addition of primary alcohols to internal alkynes (TON = 35 000, TOF = 2188 h^–1)