共查询到19条相似文献,搜索用时 201 毫秒
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一种可重复使用的非支载型金鸡纳生物碱衍生物配体与金属锇形成原位催化剂用于催化5种肉桂酸甲酯类烯烃的不对称氨羟化(AA)反应,表现了好的对映选择性(91%~96%)和反应活性(52%~72%).在以对甲基肉桂酸甲酯为底物的AA反应中,采用了两种不同的回收方法,均能有效地进行配体的回收和再利用,配体的催化活性和对映选择性基... 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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一种可回收手性配体的合成及其对烯烃不对称二羟化反应的催化性能 总被引:3,自引:0,他引:3
用1,4-二氟蒽醌与奎宁(QN)反应可高收率地得到1,4-双-(9-O-奎宁)蒽醌((QN)2AQN),再经OsO4氧化可得到带有4个羟基的手性配体. 在不对称二羟化反应的2种不同体系中,该配体对6种烯烃的反应表现出很高的对映选择性(80%~97%)和催化活性(80%~94%). 该配体不但具有金鸡纳生物碱衍生物小分子配体优异的立体选择性,同时也能象高聚物负载的大分子配体一样能够回收和重复使用,而且用量少,活性高,后处理简单. 在以反式肉桂酸乙酯为底物的不对称二羟化反应中,在t-BuOH-H2O/K3Fe(CN)6体系中循环使用5次(配体平均回收率93%),在Me2CO-H2O/NMO(N-甲基-N-氧吗啉)体系中循环使用8次,配体的催化活性和对映选择性基本保持不变. 相似文献
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1,4-双(9-O-奎宁)-2,3-二氮杂萘-OsO4催化烯烃的不对称氨羟化反应 总被引:1,自引:0,他引:1
在氧化-供氮试剂N-氯代氨基甲酸苄酯存在下,1,4-双(9-O-奎宁)-2,3-二氮杂萘-OsO4催化剂在5种烯烃的不对称氨羟化反应中表现出极高的对映选择性(85%~99%e.e.)和区域选择性,产率48%~68%. 相似文献
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一种均相催化、两相回收的手性配体的合成及其催化烯烃不对称双羟化反应 总被引:1,自引:0,他引:1
在金鸡纳生物碱衍生物配体存在下,四氧化锇催化的烯烃的不对称双羟化反应(AD)已广泛用于手性药物、精细化学品和天然产物的合成.AD反应也是合成抗癌药物紫杉醇C13-片段的实用方法之一.然而,由于配体和四氧化锇价格昂贵以及锇的毒性限制了AD反应的工业生产.近年来,在 相似文献
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在AlCl3和多聚磷酸的存在下, 以邻苯二甲酸酐和对二氟苯为原料, 通过Friedel-Crafts和环化反应, 用改进的方法以60%的产率生成1,4-二氟蒽醌. 然后通过奎宁锂与1,4-二氟蒽醌的亲核取代反应得到新型手性配体(QN)2AQN, 产率85%. 在氧化-供氮试剂N-氯代氨基甲酸苄酯存在下, (QN)2AQN与OsO4原位生成的催化剂在五种肉桂酸甲酯的不对称氨羟化反应中表现出优异的对映选择性(90%~96% ee)和一般至优秀的区域选择性(75∶25~98∶2), 产率50%~70%, 高于文献报道的结果. 该手性配体易于合成, 成本低廉, 用于催化不对称氨羟化反应, 可以制备光学活性的α-氨基酸酯类化合物. 相似文献
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Rhodium/Chiral Diene‐Catalyzed Asymmetric 1,4‐Addition of Arylboronic Acids to Chromones: A Highly Enantioselective Pathway for Accessing Chiral Flavanones 下载免费PDF全文
Qijie He Dr. Chau Ming So Prof. Dr. Zhaoxiang Bian Prof. Dr. Tamio Hayashi Prof. Dr. Jun Wang 《化学:亚洲杂志》2015,10(3):540-543
Chromone has been noted to be one of the most challenging substrates in the asymmetric 1,4‐addition of α,β‐unsaturated carbonyl compounds. By employing the rhodium complex associated with a chiral diene ligand, (R,R)‐Ph‐bod*, the 1,4‐addition of a variety of arylboronic acids was realized to give high yields of the corresponding flavanones with excellent enantioselectivities (≥97 % ee, 99 % ee for most substrates). Ring‐opening side products, which would lead to erosion of product enantioselectivity, were not observed under the stated reaction conditions. 相似文献
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Lukas J. Goossen Hong Liu K. Ruprecht Dress K. Barry Sharpless 《Angewandte Chemie (International ed. in English)》1999,38(8):1080-1083
The suprafacial, vicinal addition of a heterocyclic moiety and a hydroxyl group is achieved by the osmium-catalyzed asymmetric aminohydroxylation (AA) of olefins with amino-substituted heterocycles as the nitrogen sources. Amino alcohols are obtained in up to 97 % yield and with up to 99 % ee when a ligand derived from dihydroquinidine (DHQD-L) is used [Eq. (1); Ri indicates the remaining portion of the heterocycle (Het); H2O is the O source]. The AA can now be considered as a means to directly introduce complex, biologically relevant substructures to hydrocarbon backbones. 相似文献
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Haoke Chu Jie Cheng Junfeng Yang Prof. Dr. Yin-Long Guo Prof. Dr. Junliang Zhang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22175-22180
A palladium-catalyzed intermolecular dynamic kinetic asymmetric dearomatization of 3-arylindoles with internal alkynes was developed with the use of achiral Xantphos and chiral sulfinamide phosphine ligand ( PC-Phos ) as the co-ligands. This method could deliver various spiro[indene-1,3′-indole] compounds in good yields (up to 95 % yield) with up to 98 % ee. The salient features of the transformation include the use of readily available substrates, ease of scale-up and the versatile functionalization of the products. The mechanistic experiments gave some insights on active intermediates. 相似文献
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Organocatalytic Asymmetric Mannich-Type Reaction of Isocyanoacetates with N-(2-Benzothiazolyl)imines
Ting Yang Shuang Yan Zhe-Jia Yu Dr. Xiao-Li Zhao Prof. Min Shi Dr. Mei-Xin Zhao 《European journal of organic chemistry》2023,26(26):e202300275
An organocatalytic asymmetric synthesis of directly linked benzothiazole-dihydroimidazoles with two adjacent tertiary-quaternary stereocenters through a Mannich-type reaction of isocyanoacetates with N-(2-benzothiazolyl)imines is disclosed. When employing bifunctional dihydroquinine-derived squaramide as catalyst, moderate to excellent yields (up to 97 % yield), moderate diastereoselectivities and excellent enantioselectivities (up to >99 % ee) were obtained for a variety of substrates. In addition, the transformation of the resulted directly linked benzothiazole-dihydroimidazole into highly functionalized α,β-diamino esters was also demonstrated. 相似文献
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The 4,5‐methano‐L‐proline was used as chiral organocatalysts in direct asymmetric aldol reactions. Under the optimal conditions, excellent enantioselectivities (up to 99% ee) were obtained with high chemical yields (up to 95%) for a series of aldehydes using only 5 mol% catalyst loading. To show the practicality of the method, the reaction was tested at a large scale. The reaction was complete in 16 h, and the aldol product was obtained in 86% yield and 93% ee. 相似文献
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Zhenling Chen Dr. Lili Lin Min Wang Prof. Dr. Xiaohua Liu Prof. Dr. Xiaoming Feng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(23):7561-7567
The asymmetric Kinugasa reaction was performed on pure water for the first time without the need for any organic co‐solvents. In contrast to most asymmetric Kinugasa reactions, trans‐β‐lactams were obtained as the major products in good yields, enantioselectivities, and diastereoselectivities (up to 90 % yield, 98 % ee, and >99:1 d.r.). This reaction is atom‐economical, environmentally friendly, and affords synthetically useful but challenging products. 相似文献