Polyoxometalate catalysts:: Toward the development of green H2O2-based epoxidation systems
Polyoxometalate catalysts:: Toward the development of green H2O2-based epoxidation systems
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DOI：
10.1002/tcr.20067
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发表时间：
2006-01-01
期刊：
影响因子：
6.6
通讯作者：
Yamaguchi, K
中科院分区：
文献类型：
--
作者：
Mizuno, N;Yamaguchi, K
本文介绍了使用三种多金属氧酸盐开发绿色、高效的基于 H2O2 的环氧化体系：(i) 双核过氧钨酸盐 [W2O3(O-2)(4)(H2O)(2)](2-) (I)，(ii) 双空位多氧钨酸盐 [gamma-SiW10O34(H2O)(2)](4) (11)， (iii)和二钒取代的多钨酸盐[γ-1,2-H2SiV2W10O40](4-)(III)。 I (K-I) 的钾盐可以有效地催化各种烯丙醇在水中仅用 1 当量 H2O2 进行的高度化学、区域和非对映选择性环氧化。催化剂K-I可以在保持催化性能的情况下回收利用。双空位多钨酸[gamma-SiW10O36](8-) 的质子化得到[gamma-SiW10O34(H2O)(2)](4-) (II) 和两个水配体。 II 的四正丁基铵盐 (TBA-II) 催化包括丙烯在内的常见烯烃的环氧化，环氧化物选择性 >= 99%，H2O2 利用效率 >= 99%。 [γ-1,2-H2SiV2W10O40](4-)(III)中的双(mu-羟基)桥联二氧钒位点也可以有效地催化多种烯烃与I当量H2O2的环氧化反应。值得注意的是，具有III的体系对顺式烯烃的环氧化表现出独特的立体专一性、非对映选择性和区域选择性，分别是3-取代的环己烯和非共轭二烯，它们与迄今为止报道的环氧化体系有很大不同。此外，通过使用离子液体改性的SiO2作为载体，可以实现上述多金属氧酸盐的多相化，而不损失催化性能。 (c) 2006 年日本化学期刊论坛和 Wiley periodicals, Inc.
This paper describes the development of green, efficient H2O2-based epoxidation systems with three kinds of polyoxometalates: (i) a dinuclear peroxotungstate [W2O3(O-2)(4)(H2O)(2)](2-) (I), (ii) a divacant lacunary polyoxotungstate [gamma-SiW10O34(H2O)(2)](4) (11), (iii) and a divanadium-substituted polyoxotungstate [gamma-1,2-H2SiV2W10O40](4-) (III). The highly chemo, regio-, and diastereoselective epoxidation of various allylic alcohols with only 1 equiv H2O2 in water can be efficiently catalyzed by potassium salt of I (K-I). The catalyst K-I can be recycled with the retention of the catalytic performance. Protonation of a divacant lacunary polyoxotungstate [gamma-SiW10O36](8-) gives [gamma-SiW10O34(H2O)(2)](4-) (II) with two aquo ligands. The tetra-n-butylammonium salt of II (TBA-II) catalyzes epoxidation of common olefins including propylene with >= 99% selectivity to epoxide and >= 99% efficiency of H2O2 utilization. The bis(mu-hydroxo) bridged dioxovanadium site in [gamma-1,2-H2SiV2W10O40](4-) (III) can also efficiently catalyze epoxidation of a variety of olefins with I equiv H2O2.. Notably, the system with III shows unique stereospecificity, diastereoselectivity, and regioselectivity for the epoxidation of cisl trans olefins, 3-substituted cyclohexenes, and nonconjugated dienes, respectively, which are quite different from those reported for epoxidation systems up to now. Furthermore, the heterogenization of the mentioned polyoxometalates can be achieved by using ionic liquid-modified SiO2 as a support without loss of catalytic performance. (c) 2006 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.