New polymer-immobilized peroxotungsten compound as an efficient catalyst for selective and mild oxidation of sulfides by hydrogen peroxide

A new polymer-bound peroxotungstate(VI) catalyst of the type [W(O)2(O2)(CN)2]–PAN [PAN = poly(acrylonitrile)] (PANW) has been prepared by reacting H2WO4 with 30% H2O2 and the macromolecular ligand, PAN at pH 5.0. The compound was characterized by elemental analysis, SEM, EDX, TGA and spectral studies (FTIR and 13C NMR). Clean conversion of a variety of sulfides and dibenzothiophene (DBT) to the corresponding sulfoxide or sulfone, using H2O2 as oxidant, could be achieved in the presence of the heterogeneous catalyst PANW, by a versatile variation of reaction conditions. The reactions proceed under mild conditions to afford the resulting products with impressive turn over frequency (TOF). The catalyst exhibit complete chemoselectivity toward sulfur group of substituted sulfides with other oxidation prone functional groups. Easy regeneration and reusability of the catalyst for at least up to seven catalytic cycles with consistent activity and selectivity is an important attribute of the catalyst.

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► A new W(VI) catalyst has been developed by incorporating peroxotungsten(VI) species into poly(acrylonitrile) matrix.
► The catalyst efficiently mediates selective oxidation of various sulfides and dibenzothiophene by H2O2 to sulfoxide or sulfone.
► The oxidations take place under mild conditions with high TOF.
► The catalyst can be recovered and reused at least for seven reaction cycles with consistent activity and selectivity.