Thiolate Bridged Gold(I) NHC Catalysts: New Approach for Catalyst Design and its Application Trapping Catalytic Intermediates, Visbal, R.; Herrera, R. P.; Gimeno, M. C. Chem. Eur. J. 2019, https://doi.org/10.1002/chem.201903494
Abstract. Novel dinuclear N ‐heterocyclic gold complexes with bridging thiolate ligands have been designed to be catalytic precursors with desired properties such as stability, recyclability and the no necessity of additives. The dinuclear species [(AuNHC) 2 (µ‐SC 6 F 5 )]OTf are complexes that could slowly release the active catalytic species AuNHC + and the precursor [Au(SC 6 F 5 )(NHC)] in solution, which means that both species would maintain stable during all catalytic cycle and the pre‐catalyst could easily be recovered. These properties shown by the complexes have been taken advantage to get new insights in the gold catalyzed hydroalkoxylation of alkynes, with the aim of clarifying all the steps of the catalytic cycle, together with the characterization of intermediates and final products. Isolation and characterization of the pure final spiroketals and the thermodynamic intermediate have been achieved for the first time. Moreover, the kinetic intermediate has been also detected for the first time.
Keywords. N-Heterocyclic carbenes, gold catalysis, hydroalkoxylation reactions, reaction mechanism, cyclization reactions