Cycloisomerization versus Hydration Reactions in Aqueous Media: A Au(III)-NHC Catalyst That Makes the Difference
摘要:
A novel water-soluble Au(III)-NHC complex has been synthesized and successfully applied in the intramolecular cyclization of gamma-alkynoic acids into enol-lactones under biphasic toluene/water conditions, thus representing a rare example of an active and selective catalyst for this transformation In aqueous media. Remarkably, competing alkyne hydration processes were not observed, even during the desymmetrization reaction of challenging 1,6-diyne substrates. In addition, after phase separation, the water-soluble Au(III) catalyst could be recycled 10 times without loss of activity or selectivity.
Sol-Gel Immobilized N-Heterocyclic Carbene Gold Complex as a Recyclable Catalyst for the Rearrangement of Allylic Esters and the Cycloisomerization of γ-Alkynoic Acids
作者:Meritxell Ferré、Xavier Cattoën、Michel Wong Chi Man、Roser Pleixats
DOI:10.1002/cctc.201600632
日期:2016.9.7
The synthesis of a bis‐silylated (NHC)AuCl (NHC=N‐heterocycliccarbene) complex and the formation of a hybrid silica material by the sol–gel process by cogelification with tetraethylorthosilicate under fluoride catalysis are described. This material was characterized by using 29Si solid‐state NMR spectroscopy, N2 sorption measurements, electron microscopy, and elemental analysis. It was tested as a