The virtually quantitative, room temperature hydration of various terminal and internal alkynes in methanol/water requires between 0.01-0.05 mol% of [AuCl(NHC)] activated with 1.5 equiv. of silver triflate and 45 equiv. of triflic acid (both relative to gold complex) with ton of up to 300.000. Iptycenyl-substituted NHC ligands play the key role and the most efficient NHC ligand is characterized by a hemispherical shape formed by two N-pentiptycenyl substituents.
The efficient hydrohydrazidation of terminal (6a–r, 18 examples, 0.1–0.2 mol % [(NHC)Au(NTf2)], T = 60 °C) and internal alkynes (7a–j, 10 examples, 0.2–0.5 mol % [(NHC)Au(NTf2)], T = 60–80 °C) utilizing a complex with a sterically demanding bispentiptycenyl-substituted NHC ligand and the benign reaction solvent anisole, is reported.
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