共查询到20条相似文献,搜索用时 46 毫秒
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手性四面体过渡金属簇合物 总被引:3,自引:2,他引:1
过渡金属原子簇化学的迅猛发展,已使其成为近代化学的重要交叉学科之一.目前,不仅合成了大批的金属簇合物,进行了大量的表征和结构测定,而且已致力于实际应用的探索和开发.进入90年代,人们对手性药物的需求日益增大,不对称合成的重要性因此越显突出.在众多的不... 相似文献
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简要介绍了多齿胺膦金属配合物的设计合成。这些多齿配合显示了单齿胺或膦金属配合物所不具有的丰富结构类型和特殊催化性质,合成和表征了含有结构类似的双亚胺双膦钌配合物(R,R)-3和双胺双膦钌配合物(R,R)-4。配合物(R,R)-4可作为多种芳香酮不对称氢化的手性催化剂,其光学收率最高达97%。讨论了钌配合物的催化作用机理。 相似文献
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手性相转移催化剂及其不对称催化反应 总被引:10,自引:1,他引:10
综述了手性季铵盐和手性冠醚两类手性相转移催化剂及其在不对称催化反应(包括加成,取代,氧化及还原等反应)中的应用,参考文献97篇。 相似文献
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对脂肪酶催化含酯基的异核金属簇合物的水解反应进行了初步研究. 发现脂肪酶对簇合物的酯基进行水解时确有不对称效应, 同时簇骨架中的重金属使酶失活. 尽管不知道水解产物的e.e.值,但从旋光结果可以看出, 酶催化确是一条拆分手性簇合物的途径. 相似文献
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综述了钯-手性膦配体催化剂在烯烃的不对称氢氰化、不对称羰基化、不对称交叉偶联、不对称氢化硅氢化等方面的研究进展。参考文献36篇。 相似文献
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光学活性四面体过渡金属簇合物的诱导合成 总被引:1,自引:0,他引:1
报导了用手性季铵盐诱导合成SFeCoMo等手性四面体过渡金属簇合物的新方法。发现,苄基辛可宁对四面体簇合成有手性诱导作用;在不同溶剂中,手性簇产物的绝对构型不同,而且含钌簇的含光度比含铁簇的旋光度小。 相似文献
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The chemistry of frustrated Lewis pairs (FLPs) provides the most important approach for the metal‐free hydrogenation and hydrosilylations. Great progress has been achieved in this area for the past decade. Some promising results have also been obtained. This perspective article mainly focuses on the recent advances for the synthesis of chiral Lewis acidic boranes in category of three protocols, 1) hydroboration of chiral internal alkenes with Piers’ borane HB(C6F5)2; 2) in situ hydroboration of chiral alkenes or alkynes without any purification; 3) and substitution reaction of (C6F5)nBCl3–n with chiral organometallic reagents, as well as their applications in the metal‐free asymmetric hydrogenations and hydrosilylations.
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Adam Nelson 《Angewandte Chemie (International ed. in English)》1999,38(11):1583-1585
Both in the laboratory and industrially , phase-transfer catalysis offers the potential to induce asymmetry into reactions with anionic intermediates. Equation (a) provides an example (conditions: a) 10 mol % phase-transfer catalyst, BnBr, CsOH⋅H2O, PhMe, 15–24 h, −78°C). 相似文献
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Erasmus M. Vogl Harald Grger Masakatsu Shibasaki 《Angewandte Chemie (International ed. in English)》1999,38(11):1570-1577
Make your catalyst more enantioselective! The enantiomeric excess of a catalytic reaction system can sometimes be enhanced from below 10 to over 90 % by the use of suitable achiral additives. Since completely different mechanisms can influence the catalyst and reaction outcome, there is a range of additives that can be applied to improve the catalyst efficiency for a variety of organic reactions. 相似文献
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Dr. Yin Zhang Dr. Songbo Chen Prof. Abdullah M. Al-Enizi Prof. Ayman Nafady Prof. Zhiyong Tang Prof. Shengqian Ma 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(2):e202213399
Asymmetric hydrogenation, a seminal strategy for the synthesis of chiral molecules, remains largely unmet in terms of activation by non-metal sites of heterogeneous catalysts. Herein, as demonstrated by combined computational and experimental studies, we present a general strategy for integrating rationally designed molecular chiral frustrated Lewis pair (CFLP) with porous metal–organic framework (MOF) to construct the catalyst CFLP@MOF that can efficiently promote the asymmetric hydrogenation in a heterogeneous manner, which for the first time extends the concept of chiral frustrated Lewis pair from homogeneous system to heterogeneous catalysis. Significantly, the developed CFLP@MOF, inherits the merits of both homogeneous and heterogeneous catalysts, with high activity/enantio-selectivity and excellent recyclability/regenerability. Our work not only advances CFLP@MOF as a new platform for heterogeneous asymmetric hydrogenation, but also opens a new avenue for the design and preparation of advanced catalysts for asymmetric catalysis. 相似文献
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Johannes F. Teichert Ben L. Feringa Prof. Dr. 《Angewandte Chemie (International ed. in English)》2010,49(14):2486-2528
Asymmetric catalysis with transition‐metal complexes is the basis for a vast array of stereoselective transformations and has changed the face of modern synthetic chemistry. Key to this success has been the design of chiral ligands to control the regio‐, diastereo‐, and enantioselectivity. Phosphoramidites have emerged as a highly versatile and readily accessible class of chiral ligands. Their modular structure enables the formation of ligand libraries and easy fine‐tuning for a specific catalytic reaction. Phosphoramidites frequently show exceptional levels of stereocontrol, and their monodentate nature is essential in combinatorial catalysis, where a ligand‐mixture approach is used. In this Review, recent developments in asymmetric catalysis with phosphoramidites used as ligands are discussed, with a focus on the formation of carbon–carbon and carbon–heteroatom bonds. 相似文献
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Christina Moberg 《Angewandte Chemie (International ed. in English)》1998,37(3):248-268
Rotational symmetry can be an important factor in the design of highly selective receptors for chiral recognition. This is well known for C2-symmetric compounds, but the concept can be extended to chiral compounds of higher symmetry such as 1 . 相似文献
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Masakatsu Shibasaki Hiroaki Sasai Takayoshi Arai 《Angewandte Chemie (International ed. in English)》1997,36(12):1236-1256
This review focuses on a new concept in catalytic asymmetric reactions that was first realized for the use of heterobimetallic complexes. As these heterobimetallic complexes function as both a Brønsted base and as a Lewis acid, just like an enzyme, they make possible a variety of efficient catalytic asymmetric reactions. This heterobimetallic concept should prove to be applicable to a variety of new asymmetric catalyses. The first part of this review describes the development of rare-earth–alkali metal complexes such as LnM3tris(binaphthoxide) complexes (LnMB, Ln = rare-earth metal, M = alkali metal), which are readily prepared from the corresponding rare-earth trichlorides or rare-earth isopropoxides, and their application to catalytic asymmetric synthesis. By using a catalytic amount of LnMB complexes several asymmetric reactions proceed efficiently to give the corresponding desired products in up to 98% ee: LnLB-catalyzed asymmetric nitroaldol reactions (L = Li), LnSB-catalyzed asymmetric Michael reactions (S ? Na), and LnPB-catalyzed asymmetric hydrophosphonylations of either imines or aldehydes (P ? K). Applications of these heterobimetallic catalysts to the syntheses of several biologically and medicinally important compounds are also described. Spectral analyses and computational simulations of the asymmetric reactions catalyzed by the heterobimetallic complexes reveal that the two different metals play different roles to enhance the reactivity of both reaction partners and to position them. From mechanistic considerations, a useful activation of the heterobimetallic catalyses was realized by addition of alkali metal reagents. The second part describes the development of another type of heterobimetallic catalysts featuring Group 13 elements such as Al and Ga as the central metal. Among them, the AlLibis(binaphthoxide) complex (ALB) is an effective catalyst for asymmetric Michael reactions, tandem Michael–aldol reactions, and hydrophosphonylation of aldehydes. 相似文献