An advantageous tetrameric titanium alkoxide/ionic liquid as a recyclable catalyst system for the selective oxidation of sulfides to sulfones

The quantitative oxidation of organic sulfides to sulfones with 30% aqueous hydrogen peroxide (3:1 molar ratio of H2O2/sulfide) at room temperature using the known titanium alkoxide Ti4[(OCH2)3CMe]2(i-PrO)10 (1) as a catalyst is reported. Mixtures of sulfone/sulfoxide are obtainable with lower H2O2/sulfide ratios. Catalyst 1 can be used in a solvent, such as methanol or acetonitrile or it can be immobilized in solution in room temperature ionic liquids (RTILs), from which the product sulfone is extracted with ether, thus, allowing the 1/RTIL system to be recycled. With some substrates, approximately 30% faster reaction rates are seen in a 1/RTIL system compared with 1 in methanol.

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