Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
Dalton Trans. 2010 Jun 21;39(23):5509-18. doi: 10.1039/c002318c. Epub 2010 May 7.
The selenium-containing dinuclear peroxotungstate, (n-C(4)H(9))(4)N[SeO(4){WO(O(2))(2)}(2)] (I), acts as a homogeneous catalyst for the selective oxidation of various kinds of cyclic mono- and disulfides with 30% aqueous H(2)O(2). The cyclic disulfides were selectively oxidized to the corresponding monosulfoxides with one equivalent of H(2)O(2) with respect to the sulfides. In the presence of two equivalents of H(2)O(2), the oxidation of dibenzothiophene gave the corresponding sulfone in 98% yield under the mild conditions. The negative Hammett rho value (-0.62) for the competitive oxidation of p-substituted thioanisoles and the low X(SO) (X(SO) = (nucleophilic oxidation)/(total oxidation)) value of 0.14 for the I-catalyzed oxidation of thianthrene 5-oxide (SSO) revealed that I is a strong electrophilic oxidant. The reactivities of the di- and tetranuclear peroxotungstates with XO(4)(n-) 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 sulfoxidation decreased with an increase in the X(SO) values and a peroxotungstate with a stronger electrophilicity was more active for the sulfoxidation. The kinetic and mechanistic investigations showed that the electrophilic attack of the peroxo oxygen at the sulfur atom is a key step in the sulfoxidation. The computational investigation supported the high chemoselectivitiy for the sulfoxidation of diallyl sulfide.
含硒双核过氧钨酸盐 (n-C(4)H(9))(4)N[SeO(4){WO(O(2))(2)}(2)]（I）可作为各种环状单硫醚和双硫醚选择性氧化的均相催化剂，使用 30%的 H(2)O(2)水溶液。环状双硫醚可被 1 当量的 H(2)O(2)选择性氧化为相应的单砜。在 2 当量 H(2)O(2)的存在下，温和条件下二苯并噻吩的氧化可得到相应的砜，产率为 98%。对位取代硫代苯甲醚的竞争性氧化的负哈米特 ρ 值（-0.62）和 I 催化硫代蒽 5-氧化物（SSO）氧化的低 X(SO) 值（X(SO) =（亲核氧化）/（总氧化））0.14 表明 I 是一种强亲电氧化剂。XO(4)(n-)配体（X = Se(vi), As(v), P(v), S(vi)和 Si(iv)）的二核和四核过氧钨酸盐的反应性强烈依赖于杂原子的种类。氧化反应速率随 X(SO)值的增加而降低，具有更强亲电性的过氧钨酸盐对氧化反应更为活跃。动力学和机理研究表明，过氧氧原子对硫原子的亲电攻击是氧化反应的关键步骤。计算研究支持了二烯丙基硫醚的高化学选择性氧化。
