The selenium-contg. dinuclear peroxotungstate, [(n-C4H9)4N]2[SeO4{WO(O2)2}2] (I), acts as a homogeneous catalyst for the selective oxidn. of various kinds of cyclic mono- and disulfides with 30% aq. H2O2. The cyclic disulfides were selectively oxidized to the corresponding monosulfoxides with one equiv. of H2O2 with respect to the sulfides. In the presence of two equiv. of H2O2, the oxidn. of dibenzothiophene gave the corresponding sulfone in 98% yield under the mild conditions. The neg. Hammett ﾏ�value (-0.62) for the competitive oxidn. of p-substituted thioanisoles and the low XSO (XSO = (nucleophilic oxidn.)/(total oxidn.)) value of 0.14 for the I-catalyzed oxidn. of thianthrene 5-oxide (SSO) revealed that I is a strong electrophilic oxidant. The reactivities of the di- and tetranuclear peroxotungstates with XO4n- ligands (X = Se(vi), As(v), P(v), S(vi), and Si(iv)) were strongly dependent on the kinds of hetero atoms. The reaction rates for the sulfoxidn. decreased with an increase in the XSO values and a peroxotungstate with a stronger electrophilicity was more active for the sulfoxidn. The kinetic and mechanistic investigations showed that the electrophilic attack of the peroxo oxygen at the sulfur atom is a key step in the sulfoxidn. The computational investigation supported the high chemoselectivitiy for the sulfoxidn. of diallyl sulfide. [on SciFinder(R)]
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