Liquid-phase oxidation of a pyrimidine thioether on Ti-SBA-15 and UL-TS-1 catalysts in ionic liquids

Ti-SBA-15 and UL-TS-1 catalysts with 1.0 and 1.5 at% Ti were tested for the liquid-phase sulfoxidation of 4,6-dimethyl-2-thiomethylpyrimidine in a range of water-miscible and immiscible ionic liquids and molecular solvents. Superior rates and selectivities with respect to the sulfoxide were found in the ionic liquids compared with the molecular solvents. The activity of the catalyst was strongly dependent on the anion-cation combination chosen; the best solvent under these conditions was [emim][BF4]. Almost no leaching of titanium was found with Ti-SBA-15 in the ionic liquids, whereas significant leaching was observed in molecular solvents. In all solvents used, a surface rearrangement of titanium was observed after reaction, which may account for some loss in activity of the catalyst on recycle.