SYNTHETIC AND MECHANISTIC STUDIES ON THE ELECTROOXIDATION OF ORGANIC THIOETHERS.
AdvisorWilson, George S.
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PublisherThe University of Arizona.
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AbstractThis research has been directed at the study of neighboring group participation in electrooxidation of thioethers. Controlled potential oxidation of substituted 1,3-dithiane in wet acetonitrile provides substituted 1,2-dithiolane 1-oxide in good yield. Thioethers appended with neighboring alcohols and carboxylate are catalytically oxidized in a redox cycle by bromide ion. The formation of the alkoxysulfonium salt intermediates in such reactions is confirmed by product study. On the other hand, the acyloxysulfonium salt intermediates in the electrooxidation of endo -6-methylthio-bicyclo [2.2.1] heptane-2- endo -carboxylic acid (1) are unstable at room temperature. Control experiments using ¹⁸O labeled compounds prove unequivocally the existent of the acyloxysulfonium salt intermediates. Diastereospecific oxidation of 1 and its methyl ester with DABCO.2Br₂ complex and m-CPBA is sterically controlled. In both cases, similar product ratios are observed which is explained by the participation of the carboxylic acid group in the case of DABCO.2Br₂ oxidation but not in the case of m-CPBA oxidation. The structure of one of the diastereomer of the endo acid sulfoxide is unequivocally proved by x-ray crystallographic analysis.