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Cycloisomerization versus hydration reactions in aqueous media: a Au(III)-NHC catalyst that makes the difference
Eder Tomás-Mendivil1, Patrick Y Toullec, Josefina Díez
1Laboratorio de Compuestos Organometálicos y Catálisis (Unidad Asociada al CSIC), Departamento de Química Orgánica e Inorgánica, Universidad de Oviedo, Julián Clavería 8, E-33006 Oviedo, Spain, ChimieParisTech, Laboratoire Charles Friedel, ENSCP, UMR 7223, 11 rue P. et M. Curie, F-75231, Paris Cedex 05, France, and Departamento de Química Inorgánica, Instituto de Investigaciones Químicas (IIQ), CSIC/Universidad de Sevilla, Avda. Américo Vespucio 49, E-41092, Sevilla, Spain.
Abstract:
A novel water-soluble Au(III)-NHC complex has been synthesized and successfully applied in the intramolecular cyclization of γ-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.
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