• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Chemistry: A European journal >Efficient epoxidation of electron-deficient alkenes with hydrogen peroxide catalyzed by [γ-PW_(10)O_(38)V_2(μ-OH) _2]~(3-)
【24h】

Efficient epoxidation of electron-deficient alkenes with hydrogen peroxide catalyzed by [γ-PW_(10)O_(38)V_2(μ-OH) _2]~(3-)

机译：[γ-PW_（10）O_（38）V_2（μ-OH）_2]〜（3-）催化过氧化氢对缺电子烯烃进行高效环氧化

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

A divanadium-substituted phosphotungstate, [γ-PW_(10)O _(38)V_2(μ-OH)_2]~(3-) (I), showed the highest catalytic activity for the H_2O_2-based epoxidation of allyl acetate among vanadium and tungsten complexes with a turnover number of 210. In the presence of I, various kinds of electron-deficient alkenes with acetate, ether, carbonyl, and chloro groups at the allylic positions could chemoselectively be oxidized to the corresponding epoxides in high yields with only an equimolar amount of H_2O_2 with respect to the substrates. Even acrylonitrile and methacrylonitrile could be epoxidized without formation of the corresponding amides. In addition, I could rapidly (min) catalyze epoxidation of various kinds of terminal, internal, and cyclic alkenes with H;bsubesubbsubesub& under the stoichiometric conditions. The mechanistic, spectroscopic, and kinetic studies showed that the I-catalyzed epoxidation consists of the following three steps: 1) The reaction of I with H;bsubesubbsubesub& leads to reversible formation of a hydroperoxo species [I;circbsubesubbsubesubbsubesubcirccircbsupesup& (II), 2) the successive dehydration of II forms an active oxygen species with a peroxo group [ ~(2:2)-O_2)]~(3-) (III), and 3) III reacts with alkene to form the corresponding epoxide. The kinetic studies showed that the present epoxidation proceeds via III. Catalytic activities of divanadium-substituted polyoxotungstates for epoxidation with H _2O_2 were dependent on the different kinds of the heteroatoms (i.e., Si or P) in the catalyst and I was more active than [γ-SiW_(10)O_(38)V_2(μ-OH)_2] ~(4-). On the basis of the kinetic, spectroscopic, and computational results, including those of [γ-SiW_(10)O_(38)V _2(μ-OH)_2]~(4-), the acidity of the hydroperoxo species in II would play an important role in the dehydration reactivity (i.e., k_3). The largest k_3 value of I leads to a significant increase in the catalytic activity of I under the more concentrated conditions.
机译：二甲基取代的磷钨酸盐[γ-PW_（10）O _（38）V_2（μ-OH）_2]〜（3-）（I）对乙酸烯丙酯的H_2O_2基环氧化具有最高催化活性钒和钨的络合物，周转数为210。在存在I的情况下，烯丙基位置带有乙酸盐，醚，羰基和氯基的各种缺电子烯烃可以高收率将其化学选择性氧化为相应的环氧化物。相对于底物仅等摩尔量的H_2O_2。甚至丙烯腈和甲基丙烯腈也可以被环氧化而不形成相应的酰胺。此外，在化学计量比下，我可以快速（最小）催化H; bsubesubbsubesubsub＆与各种末端，内部和环状烯烃的环氧化。力学，光谱和动力学研究表明，I催化的环氧化反应包括以下三个步骤：1）I与H; bsubesubbsubesub＆的反应导致氢过氧物种的可逆形成[I; 2）。 II的连续脱水形成具有过氧基团[〜（2：2-O_2）]〜（3-）（III）的活性氧，并且3）III与烯烃反应形成相应的环氧化物。动力学研究表明，当前的环氧化反应通过III进行。二价取代的多氧钨酸盐对H _2O_2环氧化的催化活性取决于催化剂中杂原子的种类（即Si或P），并且我的活性比[γ-SiW_（10）O_（38）V_2（ μ-OH）_2]〜（4-）。根据动力学，光谱和计算结果，包括[γ-SiW_（10）O_（38）V _2（μ-OH）_2]〜（4-）的结果，II中氢过氧化物的酸度会在脱水反应中起重要作用（即k_3）。 I的最大k_3值导致在更浓缩条件下I的催化活性显着增加。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号