Thioethers alkoxysulfonium salts

Sulfonium salts of thiepanes are readily formed by electrophilic attack of alkyl halides on the cyclic thioether. Thus, thiepane (35) was found to yield a sulfonium iodide (123), which at elevated temperatures and in the presence of excess methyl iodide underwent ring cleavage to yield 1,6-diiodohexane (isolated as the 1,6-diphenoxy derivative Scheme 24) (53M1206). The alkoxysulfonium salt (124) formed by reaction of (35) with t-butyl hypochlorite (equation 23) was characterized as a stable hexachloroantimonate (67JOC2014). Reduction of thiepane 1-oxide (115) to thiepane has been achieved using an aqueous solution of NaHSC>3 (72JOC919). A hydroxysulfonium salt intermediate (125) has been proposed in the latter reduction reaction which provides a general method for sulfoxide reductions under mild conditions (equation 24). 

It is shown [79] that compounds VIII-X are oxidized much more easily in the presence of trace amounts of bromide ions when compared with their corresponding exo isomers, with X = COJ, CH2OH, CMe20H, Y = H. Controlled-potential electrolyses of VIII-X yield mixtures of diastereomeric sulfoxides (for VIII) or of diastereomeric alkoxysulfonium salts (for IX and X). These results are explained in terms of a neighboring carboxylate or alcohol participation in the bromide mediated oxidation of the thioethers. 

Sodium tetrahydridoborate Thioethers from alkoxysulfonium salts... 

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