Silica-Immobilized NHC-Gold(I) Complexes: Versatile Catalysts for the Functionalization of Alkynes under Batch and Continuous Flow Conditions
Immobilized sterically demanding NHC-Au(I) complexes silica-[(IPrR)Au]Cl and silica-[(IAdPrR)Au]Cl are synthesized and characterized. These complexes are suitable catalysts in typical homogeneous Au(I)-catalyzed alkyne reactions such as hydration, hydroamination, hydroarylation, or cycloisomerization. The results obtained with the immobilized catalysts in reactions in batch are comparable to those obtained with their homogeneous counterparts with the advantage of easily recovered and recycled in successive reactions. Their catalytic activity decreases when reused in batch reactions, probably because of crushing that is associated with magnetic stirring. In contrast, these immobilized cataly…
Competitive gold-activation modes in terminal alkynes: an experimental and mechanistic study.
The competition between π- and dual σ,π-gold-activation modes is revealed in the gold(I)-catalyzed heterocyclization of 1-(o-ethynylaryl)urea. A noticeable effect of various ligands in gold complexes on the choice of these activation modes is described. The cationic [Au(IPr)](+) (IPr=2,6-bis(diisopropylphenyl)imidazol-2-ylidene) complex cleanly promotes the π activation of terminal alkynes, whereas [Au(PtBu3 )](+) favors intermediate σ,π species. In this experimental and mechanistic study, which includes kinetic and cross-over experiments, several σ-gold, σ,π-gold, and other gold polynuclear reaction intermediates have been isolated and identified by NMR spectroscopy, X-ray diffraction, or …
CCDC 953983: Experimental Crystal Structure Determination
Related Article: Ana Gimeno, Ana B. Cuenca, Samuel Suárez-Pantiga, Carmen Ramírez de Arellano, Mercedes Medio-Simón, Gregorio Asensio|2014|Chem.-Eur.J.|20|683|doi:10.1002/chem.201304087
CCDC 953982: Experimental Crystal Structure Determination
Related Article: Ana Gimeno, Ana B. Cuenca, Samuel Suárez-Pantiga, Carmen Ramírez de Arellano, Mercedes Medio-Simón, Gregorio Asensio|2014|Chem.-Eur.J.|20|683|doi:10.1002/chem.201304087