Silica-bound decatungstates as heterogeneous catalysts for H2O2 activation in selective sulfide oxidation

Alkylammonium decatungstates were covalently anchored to silica gel, furnishing efficient and robust heterogeneous catalysts able to activate H2O2 in the selective oxidation of sulfide to sulfoxide. The organic-inorganic hybrid materials were fully characterized, particularly by spectroscopic experiments. Primary propylammonium decatungstate was the most active catalyst. The use of low amounts of the heterogeneous catalyst (0.1 mol%) with a slight excess of 30% H2O2 (1.15 equiv.) in a nonchlorinated solvent (methanol) makes this oxidation reaction an environmentally benign chemical process. Leaching and recycling experiments revealed that the supported catalyst is not only highly efficient but also robust, because it can be used six times without loss of activity. Furthermore, the immobilized catalyst can tolerate different types of reaction solvents. Finally, this procedure was successfully applied to various sulfides, including allyl phenyl sulfide and dibenzyl sulfide. (c) 2007 Elsevier Inc. All rights reserved.