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Abstract
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The chemoselective preparation of chiral and achiral sulfoxides is extremely important in organic chemistry. Sulfoxides are valuable intermediates for the synthesis of fine chemicals and biologically active compounds. The main synthetic route for the preparation of these valuablematerials is via oxidation of the corresponding sulfides [1].The use of ‘greenoxidants’ such as molecular oxygen andhydrogen peroxide is attractive, since they are readily available, inexpensive, and environmentally benign, with formation of wateras the only by-product [2].CaF2 is commercially available, environmentally compatible, cheap, easy to handle, and stable. It was recently shown to be agood substitute for conventional acidic catalytic materials [3].CaF2/H2O2system offers an ideal combination for the chosenoxidations. For these reasons, and in continuation of our studies onenvironmentally benign chemical processes [4],we report thechemoselective oxidation of sulfides to sulfoxides withH2O2in the presence of a catalytic amount of CaF2 under solvent-free conditions at room temperature. Various types of aromatic and aliphatic sulfides possessing functional groups such as alcohol, ester, and aldehyde are successfully and selectively oxidized without affecting sensitive functionalities. This procedure offers several major advantages: (1) the use of a commercially available, cheap, and chemically stabile catalyst and oxidant; (2) highly efficient for the selective oxidation of structurally diverse sulfides in good to high yields; (3)excellent chemoselectivity; and (4) the method conforms to several of the guiding principles of green chemistry. We believe the present method to be an improvement with respect to other procedures.
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