Gold-catalyzed oxidation of substituted phenols by hydrogen peroxide
Gold nanoparticles deposited on inorganic supports are efficient catalysts for the oxidation of various substituted phenols (2,6-di-tert-butyl phenol and 2,3,6-trimethyl phenol) with aqueous hydrogen peroxide. By contrast to more conventional catalysts such as Ti-containing mesoporous silicas, which convert phenols to the corresponding benzoquinones, gold nanoparticles are very selective to biaryl compounds (3,3′,5,5′-tetra-tert-butyl diphenoquinone and 2,2′,3,3′,5,5′-hexamethyl-4,4′-biphenol, respectively). Products yields and selectivities depend on the solvent used, the best results being obtained in methanol with yields >98%. Au offers the possibility to completely change the selectivity in the oxidation of substituted phenols and opens interesting perspectives in the clean synthesis of biaryl compounds for pharmaceutical applications.
Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (32 K)Download as PowerPoint slideResearch highlights▶ Gold nanoparticles are efficient catalysts for the oxidation of various substituted phenols by aqueous hydrogen peroxide. ▶ Gold nanoparticles are very selective to biaryl compounds and directs the reaction to C–C coupling products. ▶ Molecular oxygen from the air does not take part in the reaction and all oxygen species involved in the process result from the decomposition of H2O2 over gold particles. ▶ For a given Au content and particle size, both the reaction rate and product selectivity do not depend on the nature of the inorganic support.
Journal: Applied Catalysis A: General - Volume 387, Issues 1–2, 20 October 2010, Pages 129–134