Gold-catalyzed aerobic epoxidation of trans-stilbene in methylcyclohexane. Part I: Design of a reference catalyst

The kinetics of the heterogeneous gold-catalyzed aerobic epoxidation of stilbene in the liquid phase has been shown to be hindered by diffusion limitations, due to the use of supports which are unsuitable to apolar reaction media. The choice of these supports is generally dictated by the ability of standard methods of preparation to stabilize highly dispersed gold nanoparticles on them. Hence, new methods need to be designed in order to produce catalytically active gold nanoparticles on hydrophobic supports in general and on passivated silicas in particular. By investigating Tsukuda's method to produce colloidal solutions of gold nanoparticles upon reduction of the triphenylphosphine gold chloride complex in solution, we found that direct reduction of AuPPh3Cl in the presence of a commercially available silica support functionalized with dimethylsiloxane, Aerosil R972, leads, in a highly reproducible and potentially scalable way, to the best catalyst ever reported for this reaction.

Figure optionsDownload high-quality image (143 K)Download as PowerPoint slideHighlights
► AuPPh3Cl is successfully used as a precursor to prepare gold nanoparticles on hydrophobic silica.
► The reproducible, straight-forward, one-pot method of preparation can be scaled-up.
► Au/SiO2-Aerosil R972 is the first reference catalyst for gold-catalyzed aerobic oxidations of alkenes in the liquid phase.