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首页> 外文期刊>Chemistry: A European journal >Poly(styrene)-Supported Co-Salen Complexes as Efficient Recyclable Catalysts for the Hydrolytic Kinetic Resolution of Epichlorohydrin
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Poly(styrene)-Supported Co-Salen Complexes as Efficient Recyclable Catalysts for the Hydrolytic Kinetic Resolution of Epichlorohydrin

机译：聚（苯乙烯）支撑的Co-Salen配合物作为环氧氯丙烷水解动力学拆分的高效可循环利用催化剂

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摘要

Here we describe an unprecedented synthetic approach to poly-(styrene)-supported chiral salen ligands by the free radical polymerization of an unsymmetrical styryl-substituted salen monomer (H_2salen = bis(salicyli-dene)ethylenediamine).The new method allows for the attachment of salen moieties to the polymer main chain in a flexible,pendant fashion,avoiding grafting reactions that often introduce ill-defined species on the polymers.Moreover,the loading of the salen is controlled by the copolymerization of the styryl-substituted salen monomer with styrene in different ratios.The polymeric salen ligands are metallated with cobalt(II) acetate to afford the corresponding supported Co-salen complexes,which are used in the hydrolytic kinetic resolution of rac-emic epichlorohydrin,exhibiting high reactivity and enantioselectivity.Remarkably,the copolymer-supported Co-salen complexes showed a better catalytic performance (>99% ee,54% conversion,one hour) in comparison to the homopolymeric analogues and the small molecule Co-salen complex.The soluble poly(styrene)-supported catalysts were recovered by precipitation after the catalytic reactions and were recycled three times to afford almost identical enantiomeric excesses as the first run,with slightly reduced reaction rates.
机译：在这里，我们描述了一种空前的合成方法，该方法通过不对称的苯乙烯基取代的salen单体（H_2salen =双（水杨基-二烯）乙二胺）的自由基聚合来制备聚（苯乙烯）支撑的手性Salen配体。 Salen部分以柔性，悬垂的方式连接到聚合物主链上，从而避免了接枝反应，该接枝反应经常在聚合物上引入不明确的种类。此外，Salen的负载量受苯乙烯基取代的salen单体与苯乙烯的共聚作用控制用乙酸钴（II）金属化聚合物Salen配体，得到相应的负载型Co-salen配合物，该配合物用于外消旋环氧氯丙烷的水解动力学拆分中，具有很高的反应性和对映选择性。负载的Co-salen配合物与均聚物相比具有更好的催化性能（ee> 99％，转化率54％，一小时）催化反应后，通过沉淀法回收了可溶性聚（苯乙烯）负载型催化剂，并将其循环使用三遍，得到与第一次操作几乎相同的对映体过量，反应速率略有降低。

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