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1.
四氧化锇催化的不对称双羟基化反应 总被引:1,自引:0,他引:1
本文综述了近年来四氧化锇催化不对称双羟基化的研究进展。在诸多改进的方法中以铁氰化钾为共氧化剂和以金鸡纳生物碱酯为手性配体的OsO_4催化不对称双羟化为最好,对映体过量一般在90%以上,化学产率为80—95%,我们首次将这个不对称双羟化用于构成植物生长调节剂油菜甾体的双羟基侧链,获得令人满意的结果。 相似文献
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氨基酸的不对称合成是近年来研究热点之一,双不对称合成新设想为高光学纯度物质的合成提供了一条有益的思路。本文考察在手性相转移催化条件下,邻苯二甲酰亚胺钾与手性α-溴代丙酸龙脑酯的Gabriel反应制取光学活性丙氨酸,观察到显著的双不对称诱导效应。 仪器为Perkin-Elmer 241MC型旋光仪、PE240-C型元素分析仪。邻苯二甲酰亚胺钾按文献[3]制备;α-溴代丙酸乙酯为上海试剂总厂产品,(一)-龙脑为贵州罗甸制药厂产品,[αj_D~(25)=—37.2,(C5,乙醇);α-溴代丙酸龙脑酯根据文献制备并经过元素分析和光谱鉴定。(一)-N-苄 相似文献
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不对称氢酯基化反应是不对称羰基化反应的一部分,与不对称氢甲酰化反应一样是产生多种手性分子的有力手段,比如重要的非麻醉性镇痛消炎药S-布洛芬、S-萘普生就可以通过芳香类烯烃的不对称氢酯基化反应来合成.在不对称羰基化中人们对不对称氢甲酰化的研究较为广泛,并取得了 相似文献
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含有大位阻基团的1,1-双取代α,β-不饱和酯,诸如甲基丙烯酸三苯甲酯(TrMA)、甲基丙烯酸邻甲苯基二苯基甲酯(DPIMA),在不对称聚合反应中,能够形成具有单手螺旋构象的旋光性聚合物。这类聚合物因具有独特的手性识别能力而一直为人们所瞩目。现有的研究结果表明,在这类单体的不对称聚合反应中,手性配体如鹰爪豆碱[(—)-Sp]决定着聚合产物 相似文献
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综述了近年来光学活性α-氨基膦酸及其酯的各种不对称合成方法,包括化学计量不对称合成和催化不对称合成。重点介绍了近年发展起来的催化不对称合成方法,并且对各种合成方法的优劣进行了评述。 相似文献
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利用手性双唑啉与三氟甲磺酸亚铜催化2-甲氧基苯乙烯与重氮乙酸二环己基甲酯的不对称环丙烷化反应合成了手性环丙烷羧酸酯,用氢氧化钠对其进行选择性水解得到全反式环丙烷羧酸,其ee值经GC测定为88%.进一步经过Curtius重排、烷基化等反应及重结晶等步骤合成了光学纯的具有生理活性的环丙胺化合物1a和1b. 相似文献
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β,γ-不饱和α-酮酸酯是一种多官能团的合成子,其1,2-双羰基的结构便于进行活化和手性控制,多个反应位点可以进行多样的反应设计.近20年来,许多手性路易斯酸催化剂和有机小分子催化剂被应用到β,γ-不饱和α-酮酸酯参与的不对称催化反应中,得到了各种光活性化合物.根据β,γ-不饱和α-酮酸酯中的β,γ-不饱和α-酰基共轭体系、碳碳双键及羰基三种不同的反应位点分类,对近几年来β,γ-不饱和α-酮酸酯在不对称催化中的应用进展进行综述.同时对存在的局限性和未来的发展趋势进行了展望. 相似文献
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考察了手性双膦配体DDPPI在钯催化1-辛烯及官能化端烯的不对称氢酯基化反应中的手性诱导作用,最高得到了45.2%的ee值.其中在1-辛烯的不对称氢酯基化反应中,考察了不同的膦-钯比、反应温度、压力、不同的溶剂、不同的钯催化剂前体以及助催化剂对反应的影响.其中膦,钯比在2~4的范围内,催化反应获得了较高的光学产率;以丙酮作溶剂,得到较好的催化效果. 相似文献
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A new camphor-based 2-phenylimino-2-oxazolidine chiral auxiliary was prepared and it was shown to be a particularly effective chiral auxiliary for asymmetric alkylations affording high yields and diastereoselectivities. The alkylation products were readily cleaved by simple alkaline hydrolysis to give a-alkylated carboxylic acids in good yield and in almost enatiomerically pure form. 相似文献
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Anne Brethon Catherine Bied Joël J. E. Moreau Michel Wong Chi Man 《Journal of Sol-Gel Science and Technology》2009,50(2):141-151
Bridged silsesquioxanes with asymmetric catalytic properties are described. These new silica-based materials are obtained
by the sol-gel hydrolysis of an organosilylated chiral compound bearing rhodium-complexed diphosphine ligands. The incorporation
of the organometallic species in various hybrid networks was achieved upon co-hydrolysis of the latter silylated ligands with
TEOS or with 1,4-bis(trimethoxysilyl)benzene. These amorphous hybrids have been tested as enantioselective catalysts for the
hydrogenation of (Z)α-(acetamido)cinnamic acid to the corresponding aminoacid and the results were compared with that obtained
from the complexed precursor in homogeneous medium and related grafted silica. Enantioselectivities slightly higher than for
homogeneous reaction were obtained in the case of the heterogeneous catalysts prepared by the direct hydrolysis of the rhodium-complexed
diphosphine compound or by its co-hydrolysis with 1,4-bis(trimethoxysilyl)benzene. Conversely, a significant decrease in selectivity
was observed when the organometallic species was immobilised in silica or grafted at the surface of silica. 相似文献
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Nobuyuki Mase 《Tetrahedron letters》2005,46(18):3213-3216
Chiral phase-transfer catalyzed enantioselective alkylations of tert-butyl glycinate-benzophenone Schiff base were investigated in aqueous media without any organic solvent. Reactions in aqueous media smoothly proceeded to give the desired product in higher yield than under standard liquid-liquid biphasic conditions. In aqueous media the formation of benzophenone, which was caused by in situ hydrolysis of Schiff base, was depressed. 相似文献
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Non-racemic cyanohydrin acetates are readily available from aldehydes and potassium cyanide/acetic anhydride by use of bimetallic titanium (salen) catalyst 1. Treatment of the cyanohydrin acetates with a platinum(II) phosphinito catalyst 3 under neutral conditions results in chemoselective hydrolysis to the corresponding α-acetoxy amides in a racemization free process. 相似文献
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Torsten Dwars Ute Schmidt Christine Fischer Ingrid Grassert Rhett Kempe Roland Frhlich Karlheinz Drauz Günther Oehme 《Angewandte Chemie (International ed. in English)》1998,37(20):2851-2853
Enantiomeric excesses of up to 99 % could be obtained in the synthesis of the biologically interesting acylated α-aminophosphinic acids 1 (R1=Me, Ph; R2=H, Me, Et; R3=H, F, iPr) by asymmetric hydrogenation with rhodium complex catalysts and subsequent hydrolysis [Eq. (1)]. cod=1,5-cyclooctadiene. 相似文献
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The asymmetric Favorskii rearrangement of optically active α‐haloketones, which are easily prepared from chiral menthyl‐4‐toluenesulfoxide in several steps using primary or secondary amines, yields their corresponding secondary or tertiary chiral amides. The secondary chiral amides were converted to acids or amines using acylation followed by hydrolysis or reduction. In addition, the tertiary amides were directly reduced to alcohol with Super‐Hydride®. 相似文献
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Yan Zhou 《Tetrahedron》2006,62(24):5692-5696
Asymmetric catalysis of chiral spiroborate esters with an O3BN framework toward the direct aldol reaction of acetone and aromatic aldehydes was examined, and a new, efficient chiral catalyst was discovered. In the presence of the novel catalyst, acetone was allowed to react with aromatic aldehydes at 0 °C for 50 h to afford chiral β-hydroxyketone in up to >99% ee and 92% yield. The catalyst, which is readily synthesized, is highly stable to hydrolysis, thermolysis, oxidation, and racemization, can be conveniently recovered. 相似文献
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Xiao-Bing Chen Dr. Damián Padín Charlotte N. Stindt Prof. Dr. Ben L. Feringa 《Angewandte Chemie (International ed. in English)》2023,62(33):e202307450
P-stereogenic compounds are widely used as ligands in asymmetric catalysis and are present in a myriad of bioactive compounds and pharmaceuticals. Yet, their stereocontrolled preparation remains challenging. Herein, we report a novel strategy towards versatile chiral-at-P alkenylphosphonamidates through a one-pot Ni-catalyzed C−P coupling/diastereoselective hydrolysis of readily available phosphoramidites and alkenyl halides. Remarkably, a chemo- and diastereodivergent behavior was observed upon subtle changes in the reaction conditions. Additionally, selective derivatizations of chiral alkenylphosphonamidates demonstrate their versatility as building blocks for the synthesis of structurally diverse P-stereogenic compounds. 相似文献
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FUYing-huan CHENJin WUTong-hao BAIXu 《高等学校化学研究》2005,21(4):476-479
To investigate the recovery of amino alcohols as chiral auxiliaries, optically active p-benzyloxyphenylglycinol and its corresponding oxazolidine of 1-naphthylcarboxaldehyde were prepared. Grignard additions to the oxazolidine followed by electrophilic quench and acidic hydrolysis afforded an aldehyde( compound 8) (later it was reduced to an alcohol, compound 9) in an excellent enantiomeric excess and a good recovery of the chlral amino alcohol. This research provides a model study of chiral amino alcohols in solid phase asymmetric synthesis. 相似文献