共查询到20条相似文献,搜索用时 93 毫秒
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不对称氢化反应;聚合物;金鸡纳生物碱-丙烯酸甲酯共聚物及其水解型聚合物的合成 相似文献
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以3,6-二氯哒嗪为桥联基与奎宁及二氢奎宁在NaH和DMF中反应,生成物奎宁一侧在AIBN存在下与巯基乙醇反应,进而氧化成砜.生成的金鸡纳生物碱衍生物新配体1在AD反应中对6种烯烃的二羟化反应表现了很高的对映选择性(88%~99%e.e.)和化学产率(74%~91%).配体1可以回收和重复使用,在以肉桂酸乙酯为底物的AD反应中,重复使用4次,其催化活性和对映选择性保持不变. 相似文献
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金鸡纳生物碱的金属络合物用于苯乙酮的不对称催化还原 总被引:3,自引:0,他引:3
金鸡纳生物碱的金属络合物用于苯乙酮的不对称催化还原刘湘(无锡轻工大学化工系无锡214036)李纪国张正(南京大学化学系南京210093)关键词金鸡纳生物碱手性络合物不对称还原苯乙酮分类号O643.32近10多年来,前手性酮的不对称还原反应作为制备光学... 相似文献
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金鸡纳生物碱衍生手性双胺配体的合成及其在不对称氢转移反应中的催化作用 总被引:1,自引:0,他引:1
以价廉易得的天然金鸡纳生物碱奎宁和辛可宁为原料,在温和条件下容易地合成了6种手性双胺配体. 考察了它们与过渡金属Ir和Rh形成的配合物在苯乙酮不对称氢转移反应中的催化活性和不对称诱导作用. 结果表明, 9-氨基金鸡纳生物碱配体具有良好的不对称催化活性,而当配体中的氨基被取代后其对映选择性降低. 将9-氨基(9-脱氧)表辛可宁的Ir配合物用于其它芳香酮的不对称氢转移反应时,该配体也显示了很高的催化活性(80%~90%收率)和对映选择性(除对氯苯乙酮ee值为72%外,其余芳香酮ee值均为95%~97%). 相似文献
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Origins of enantioselectivity in reductions of ketones on cinchona alkaloid modified platinum 总被引:2,自引:0,他引:2
A model to explain the stereoselectivities of reductions of activated ketones on cinchona alkaloid modified platinum is proposed and is supported by calculations by density functional and force field methods. The model involves nucleophilic catalysis by the cinchona alkaloid. The zwitterionic adduct between a cinchona alkaloid and ketone is adsorbed on Pt through the quinoline ring and two heteroatoms and is subsequently reduced with inversion. The model rationalizes the observed stereoselectivities for hydrogenation of carbonyl compounds. 相似文献
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Sobhani S Fielenbach D Marigo M Wabnitz TC Jørgensen KA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(19):5689-5694
The application of cinchona alkaloid derivatives as catalysts for enantioselective alpha-sulfenylation of activated C-H bonds in lactones, lactams, and beta-dicarbonyl compounds by different electrophilic sulfur reagents is presented. Optically active products are obtained in good to excellent yields and up to 91 % ee. Furthermore, the diastereoselective reduction of alpha-sulfenylated beta-keto esters to give optically active alpha-sulfenylated beta-hydroxy esters has been studied. A model for the intermediate is presented, in which the protonated cinchona alkaloid interacts with the substrate leading to face-shielding in accordance with the enantioselective alpha-sulfenylation step. 相似文献
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Garret M. Miyake Hiroki Iida Hai‐Yu Hu Zhenglin Tang Eugene Y.‐X. Chen Eiji Yashima 《Journal of polymer science. Part A, Polymer chemistry》2011,49(24):5192-5198
Four novel dynamic helical poly(phenylacetylene)s bearing cinchona alkaloids as pendant groups were synthesized starting from the commercially available cinchona alkaloids, cinchonidine, cinchonine, quinine, and quinidine, by the polymerization of the corresponding phenylacetylene monomers with a rhodium catalyst. These polymers exhibited an induced circular dichroism (ICD) in the UV–visible region of the polymer backbones in solution, resulting from the preferred‐handed helical conformation induced by the optically active cinchona alkaloid pendants. In response to the solvent used, their Cotton effect patterns and intensities were significantly changed accompanied by the changes in their absorption spectra probably due to the changes in their helical conformations, such as the inversion of the helical sense or helical pitch of the polymers. When these helical polymers were used as polymeric organocatalysts for the asymmetric conjugated addition and Henry reactions, the optically active products with a modest enantiomeric excess were obtained whose enantioselectivities were comparable to those obtained with the corresponding cinchona alkaloid‐bound monomers as the catalysts. However, we observed a unique enhancement of the enantioselectivity and a reversal of the stereoselectivity for some helical polymers, suggesting the important role of the helical chirality during the asymmetric organocatalysis. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
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Shi-Kai Tian 《Tetrahedron》2006,62(49):11320-11330
A highly enantioselective cyanocarbonation of dialkyl ketones catalyzed by commercially available and easily recyclable cinchona alkaloid derivatives has been developed. The reaction provides a useful approach for the enantioselective construction of tetrasubstituted carbon stereocenters. Mechanistic studies have been carried out to shed light on the origin of the catalytic activity of the cinchona alkaloid and the asymmetric induction step. 相似文献
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Song Bai Xueping Liang Baoan Song Pinaki S. Bhadury Deyu Hu Song Yang 《Tetrahedron: Asymmetry》2011,22(5):1730-523
An efficient one-pot synthesis of novel β-amino ester derivatives containing a benzoxazol moiety has been developed by using cinchona alkaloid thioureas as the organocatalyst. The adducts were isolated in high enantiomeric excess and high yield. 相似文献
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Dogo-Isonagie C Bekele T France S Wolfer J Weatherwax A Taggi AE Lectka T 《The Journal of organic chemistry》2006,71(23):8946-8949
The optimization of a practical, catalytic, asymmetric process for the alpha-bromination of acid chlorides to produce synthetically versatile, optically active alpha-bromoesters is reported. A range of products is produced in high enantioselectivity and moderate to good chemical yields with retention of both upon scale-up. The reactions herein are catalyzed by cinchona alkaloid derivatives, with the best performance achieved by the use of a proline cinchona alkaloid conjugate designed in a de novo fashion. 相似文献
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A series of cyclodextrin-cinchona alkaloid inclusion complexes were prepared from beta-cyclodextrin, heptakis(2,6-di-O-methyl)-beta-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin and four cinchona alkaloids in ca. 90% yields, and their inclusion complexation behavior was investigated at pH 7.2 and 1.5 by means of fluorescence, UV/Vis and 2D NMR spectroscopy. The results showed that the cinchona alkaloids can be efficiently encapsulated in the cyclodextrin cavity in an acidic environment and sufficiently released in a neutral environment, which makes these cyclodextrin derivatives the potential carriers for cinchona alkaloids. The binding ability and molecular selectivity of cyclodextrins toward cinchona alkaloids were discussed from the viewpoint of the size-fit concept and multiple recognition mechanism between host and guest. 相似文献
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Discovery and Application of Doubly Quaternized Cinchona‐Alkaloid‐Based Phase‐Transfer Catalysts 下载免费PDF全文
Bangping Xiang Kevin M. Belyk Robert A. Reamer Nobuyoshi Yasuda 《Angewandte Chemie (International ed. in English)》2014,53(32):8375-8378
We report the discovery of novel N,N′‐disubstituted cinchona alkaloids as efficient phase‐transfer catalysts for the assembly of stereogenic quaternary centers. In comparison to traditional cinchona‐alkaloid‐based phase‐transfer catalysts, these new catalysts afford substantial improvements in enantioselectivity and reaction rate for intramolecular spirocyclization reactions with catalyst loadings as low as 0.3 mol % under mild conditions. 相似文献
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The role that the nature of the solvent plays in defining the extent of cinchona alkaloid adsorption-desorption equilibrium on platinum surfaces has been studied both by testing their solubility in 54 different solvents and by probing the stability of adsorbed cinchona in the presence of those solvents. The solubilities vary by as much as 5-6 orders of magnitude, display volcano-type correlations with solvent polarity and dielectric constant, and follow a cinchonine < cinchonidine < quinine, quinidine sequence. The adsorption-desorption equilibrium shifts toward the solution with increasing dissolving power of the solvent. The relevance of these results to the behavior of cinchona as chiral modifiers in hydrogenation catalysis is discussed. 相似文献