Novel sulfonated N-heterocyclic carbene gold(I) complexes: Homogeneous gold catalysis for the hydration of terminal alkynes in aqueous media

摘要

A series of novel water-soluble Au~I complexes using sulfonated N-heterocyclic imidazolylidene carbenes as ligands was prepared by transmetalation from the corresponding bis-carbene Ag~I complexes. Monocarbene Au~I complexes were employed as catalysts in the hydration of terminal alkynes in aqueous media. Hydrations proceeded selectively according to Markovnikovs 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 (H_2SO_4, AgOTs, AgBF_4, NaOH) were examined. Corresponding bis-carbene Au~I complexes were also isolated and characterized. However, these exhibit no catalytic activity in the explored systems.