Novel Sulfonated N-Heterocyclic Carbene Gold(I) Complexes: Homogeneous Gold Catalysis for the Hydration of Terminal Alkynes in Aqueous Media

A series of novel water-soluble AuI complexes using sulfonated N-heterocyclic imidazolylidene carbenes as ligands was prepared by transmetalation from the corresponding bis-carbene AgI complexes. Monocarbene AuI complexes were employed as catalysts in the hydration of terminal alkynes in aqueous media. Hydrations proceeded selectively according to Markovnikov’s rule with high rates and turnover numbers (up to TON 935). The highest activity was achieved in hydration of p-ethynylanisole (TOF = 400.2 h−1). Effects of additives (H2SO4, AgOTs, AgBF4, NaOH) were examined. Corresponding bis-carbene AuI complexes were also isolated and characterized. However, these exhibit no catalytic activity in the explored systems.