Copper-catalyzed three-component tandem amination/cyanation/alkylation of the primary-amine-tethered alkynes 1 gave α-CN-substituted pyrrolidines 6 in good yields and regioselectivities. In addition, silver-mediated tandem amination/oxidation of the secondary-amine-tethered alkynes 7 produced functionalized pyrroles 8 in good yields. All reactions were conducted in one pot without any protection/deprotection steps.

Gold catalysts capable of promoting reactions at low-level loadings under mild conditions are the exception rather than the norm. We examined reactions where the regeneration of cationic gold catalyst (e.g., protodeauration) was the turnover limiting stage. By manipulating electron density on the substituents around phosphorus and introducing steric handles we designed a phosphine ligand that contains two electron-rich ortho-biphenyl groups and a cyclohexyl substituent. This ligand formed a gold complex that catalyzed common types of gold-catalyzed reactions including intra- and intermolecular XH (X=C, N, O) additions to alkynes and cycloisomerizations, with high turnover numbers at room temperature or slightly elevated temperatures (≤50 °C). Our new ligand can be prepared in one step from commercially available starting materials.

The first detailed experimental study of the deactivation of cationic gold was conducted, and the influence of each component in the reaction system (substrate, counterion, solvent) on the decay process was examined. It was found that a substrate (alkyne/allene/alkene)-induced disproportionation of gold(I) may play a key role in the decay process. Our mechanism is supported by kinetic, XPS, voltammetry studies, and high-resolution ESI-MS data.