共查询到20条相似文献,搜索用时 15 毫秒
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手性金属配合物催化剂在不对称合成中占有重要地位[1-3]。在该类催化剂参与的不对称催化反应中,配合物中手性配体是催化反应立体选择性优劣的关键[4,5]。为了改进该类催化剂的性能,主要对手性配体进行过化学修饰。目前合成的手性催化剂几乎都是由同一种手性配体和一种金属离子组成的二元配合物,且高效者并不多.文献[6]曾提到有关手性三元配合物(亦称手性混合配体配合物)。在不对称催化中应用的可能性,但未见具体报道。本文以中性含氮配体和含氧酸与铜(Ⅱ)配位合成了一类手性三元铜(Ⅱ)配合物及其在不对称合成菊酸中的催化性能。 相似文献
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The design of new chiral ligands is the key in the development of transition metal catalyzed asymmetric synthesis. Many chiral diphosphine ligands have been prepared and applied in asymmetric catalytic reactions with excellent enantioselectivities. Among the chiral diphosphine ligands that have been reported, the atropisomeric C2-symmetric phosphines with a biaryl scaffold initiated by Noyori and co-workers with BINAP were found to have the widest application in the transition metal catalyze… 相似文献
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Heimo Wölfle Klaus Wurst Hans-Helmut Görtz Benno Bildstein 《Journal of organometallic chemistry》2006,691(6):1197-1215
We report on novel chiral tridentate [NO2]H2 and tetradentate [N2O2]H2 Schiff base ligands containing a planar chiral ferrocene moiety linked to hydroxyl-imine or diimine donors with central or axial chirality. Structurally, these ligands resemble half-salen and salen systems designed for stereoselective applications of their transition metal complexes in homogeneous catalysis. The modular synthesis involves diastereoselective metalation of chiral ferrocene or pentamethylferrocene acetals, followed by stereoconservative hydroxyalkylation and condensation with chiral hydroxyamines or diamines, respectively. In comparison to salen-type systems, an important advantage of these ligands is their tunable steric protection of the alkoxide donor site. A total of 18 different ligands varying in electronic and steric properties have been prepared and fully characterized by NMR, IR, mass spectroscopy and by single crystal structure analysis of nine precursors and representatives. 相似文献
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A family of chiral molecular squares based on fac-Re(CO)3Cl metallocorners and enantiopure atropisomeric bipyridine bridging ligands (L1-4) have been synthesized in high yields by refluxing ClRe(CO)5 and L1-4 in 1:1 molar ratio. These novel chiral metallocycles have been characterized by 1H and 13C{1H} NMR, UV-vis, luminescence, and circular dichroism (CD) spectroscopies, FAB mass spectrometry, and microanalysis. Molecular square 4 which contains four 1,1'-bi-2-naphthol functionalities exhibits interesting enantioselective luminescence quenching by 2-amino-1-propanol. This research illustrates the potential of generating novel functional materials based on supramolecular chemistry. 相似文献
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LIU YuanYuan YANG GuoQiang YAO DongMei TIAN FengTao & ZHANG WanBin School of Chemistry Chemical Engineering Shanghai Jiao Tong University Shanghai China 《中国科学B辑(英文版)》2011,(1)
Tropos phosphine-oxazoline ligands have shown interesting coordination behavior and excellent chiral inducing ability in asymmetry catalysis.Here we present a convenient and economic route for the synthesis of this type of ligands.According to this new route,the ligands with different electronic and steric properties have been prepared successfully. 相似文献
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Doris Domin Kurt Mereiter Johannes Fröhlich Karl Kirchner 《Journal of organometallic chemistry》2007,692(5):1048-1057
The synthesis and characterization of a range of chiral β-diimine ligands and their complexes with palladium(II) has been investigated. The introduction of chirality can be easily achieved through a combination of both achiral and chiral building blocks. The absolute configuration of the stereochemical centers has been determined. In addition, representative X-ray structures of both ligands and complexes have been determined. 相似文献
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A new class of chiral pyrrolidine ligands have been successfully synthesized and their chiral induction abilities have been examined in the homogeneous catalytic enantioselective cyclo-propanation of styrene. 15-30% enantiomeric excess ( ee) has been achieved. 相似文献
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Cheruku P Paptchikhine A Ali M Neudörfl JM Andersson PG 《Organic & biomolecular chemistry》2008,6(2):366-373
New thiazole-based chiral N,P-ligands that are open-chain analogues of known cyclic thiazole ligands have been synthesized and evaluated in the iridium-catalyzed asymmetric hydrogenation of trisubstituted olefins. Chirality was introduced into the ligands through a highly diastereoselective alkylation using Oppolzer's camphorsultam as chiral auxiliary. In general, the new catalysts are as reactive and selective as their cyclic counterparts for the asymmetric hydrogenation of various trisubstituted olefins. 相似文献
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金属催化的不对称氢化反应研究进展与展望 总被引:1,自引:0,他引:1
手性过渡金属络合物催化的不对称氢化反应是合成光学活性化合物的重要方法. 本文从手性配体及手性催化剂、不对称催化新反应、新方法和新策略三个方面简要评述新世纪以来过渡金属催化的不对称氢化反应研究领域的新进展. 从新世纪初至今, 手性单磷配体得到了复兴, 出现了如MonoPhos、SiPhos、DpenPhos等高效单齿亚磷酰胺酯配体; 磷原子手性(P-手性)配体也得到了快速发展, 如BenzP*、ZhanPhos、TriFer等已成为新的高效手性双膦配体; 螺环骨架手性配体成为新世纪手性配体设计合成的亮点, 除了SiPhos、SIPHOX、SpinPHOX等高效手性螺环配体外, 手性螺环吡啶胺基磷配体SpiroPAP的铱催化剂成为目前最高效的分子催化剂. 不对称催化氢化新反应研究也取得了突破, 如非保护烯胺、杂芳环化合物及N-H亚胺的氢化等反应都实现了高对映选择性. 自组装手性催化剂、树枝状手性催化剂、铁磁性纳米负载的可回收手性催化剂, 以及“混合”配体手性催化剂等新方法和新策略也在不对称催化氢化反应中得到了应用. 然而, 手性过渡金属络合物催化的不对称氢化研究仍然充满挑战, 也期待新的突破. 相似文献
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Hanne Therese Bonge 《Tetrahedron letters》2010,51(41):5375-4203
Three new chiral Rh(II) catalysts with 4-hydroxyproline-derived ligands have been synthesised through a short and efficient synthetic route. The catalysts give good yields and ees in C-H insertion and cyclopropanation reactions, and their properties indicate an all-up reactive conformation of proline- and 4-hydroxyproline-derived Rh(II) catalysts. 相似文献
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Some new chiral cyclohexyl based fluorescent anion receptors have been synthesized and their absolute configuration has been determined by using circular dichroism (CD). Complexation experiments have been carried out with several dicarboxylates, and stoichiometries and complexation constants for the corresponding complexes have been determined. The chiral discrimination ability of these ligands for chiral dicarboxylates has been studied and the best results have been obtained with TMA aspartate. 相似文献
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Everton Machado da Silva Hrika Danielle Almeida Vidal Marcelo Augusto Pereira Janurio Arlene Gonalves Corrêa 《Molecules (Basel, Switzerland)》2023,28(1)
BINOL derivatives have shown relevant biological activities and are important chiral ligands and catalysts. Due to these properties, their asymmetric synthesis has attracted the interest of the scientific community. In this work, we present an overview of the most efficient methods to obtain chiral BINOLs, highlighting the use of metal complexes and organocatalysts as well as kinetic resolution. Further derivatizations of BINOLs are also discussed. 相似文献
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Dr. Lieby Zborovsky Dr. Hagar Tigger-Zaborov Prof. Dr. Galia Maayan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(38):9098-9107
The understanding of structure–function relationships within synthetic biomimetic systems is a fundamental challenge in chemistry. Herein we report the direct correlation between the structure of short peptoid ligands—N-substituted glycine oligomers incorporating 2,2′-bipyridine groups—varied in their monomer sequence, and the photoluminescence of RuII centers coordinated by these ligands. Based on circular dichroism and fluorescence spectroscopy we demonstrate that while helical peptoids do not affect the fluorescence of the embedded RuII chromophore, unstructured peptoids lead to its significant decay. Transmittance electron microscopy (TEM) revealed significant differences in the arrangements of metal-bound helical versus unstructured peptoids, suggesting that only the latter can have through-space interactions with the ruthenium dye leading to its quenching. High-resolution TEM enabled the remarkable direct imaging of singular ruthenium-bound peptoids and bundles, supporting our explanation for structure-depended quenching. Moreover, this correlation allowed us to fine-tune the luminescence properties of the complexes simply by modifying the sequence of their peptoid ligands. Finally, we also describe the chiral properties of these Ru–peptoids and demonstrate that remote chiral induction from the peptoids backbone to the ruthenium center is only possible when the peptoids are both chiral and helical. 相似文献
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Audrey Nowicki 《Tetrahedron letters》2005,46(10):1617-1621
Palladium catalyzed asymmetric allylic alkylation of prochiral aryl cyano esters has been carried out in the presence of various chiral ligands. The base and additives have been varied and allowed to produce the allyl derivative presenting a highly functionalized quaternary stereogenic center. The chiral pocket ligands of Trost appears the most appropriate to produce the desired chiral derivative. 相似文献
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Bidentate and tetradentate ligands containing the oxazoline unit have been successful in a range of asymmetric transformations.[1~3] Chiral tridentate ligands may form a deeper chiral concave pocket around the metal center, and have been less extensively used in asymmetric catalysis than their bidentate or tetradentate analogues. Nishiyama's tridentate "pybox"ligand, in which a pyridine ring links two chiral oxazoline moieties, has been successfully used in various asymmetric reactions. 相似文献