共查询到20条相似文献,搜索用时 515 毫秒
1.
2.
将以烯烃为原料通过Sharpless不对称双羟化等多步反应合成的8种手性β-氨基醇, 作为有机小分子催化剂, 用于催化α,β-不饱和酮的不对称环氧化反应.考察了影响对映选择性的催化剂结构、催化剂用量、氧化剂种类、溶剂、反应温度等因素.结果表明, 当催化剂用量为30 mol%、氧化剂为TBHP(叔丁基过氧化氢)、正己烷溶剂、在室温下、以(1S,2R)-(+)-1,2-二苯基-2-甲氨基乙醇(3)作催化剂时, 所得环氧化物的对映体过量最高为70% ee, 产率最高为84%. 相似文献
3.
4.
5.
6.
7.
两种邻、间手性二醇的区域选择性取代反应研究 总被引:1,自引:0,他引:1
对两种邻、间手性二醇的区域选择性取代反应进行了研究. 以(R)-(-)-1,3-丁二醇(1)为起始原料, 在各种有机碱存在下, 先合成C1-位单磺酸酯, 进行C1-位的单醚化取代, 均有非区域选择性的单(双)取代物生成. 若用SOCl2处理1, 使其首先生成环状亚硫酸酯中间体5, 苯硫酚在2% Na2CO3存在下可和其发生高区域选择性取代反应, 生成 (R)-(-)-3-羟基-丁基苯硫醚(3). 以同样的方法使(S,R)-(+)-1-(6-氟-2-色满基)-1,2-乙二醇(6)和SOCl2反应生成环状亚硫酸酯(9), 再和苄胺反应, 也可发生高区域选择性取代, 生成 (S,R)-(+)-2-苄氨基-1-(6-氟-2-色满基)-乙醇(8). 该反应方法具有高区域选择性, 产物有高旋光纯度、高产率. 相似文献
8.
9.
10.
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
11.
Rong-Hui Wang Dr. Ya-Ling Li Hong-Jiao He Prof. You-Cai Xiao Prof. Fen-Er Chen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(13):4302-4306
The catalytic enantioselective diorganozinc additions to cyclic diketones including pyrazolin-4,5-diones and isatins have been developed. In the presence of morpholine-containing chiral amino alcohol ligand, the corresponding chiral cyclic tertiary alcohols were produced in good to excellent yields (up to 97 %) and enantioselectivities (up to 95 % ee). The notable feature of this protocol includes its mild reaction conditions, Lewis acid additives free and broad functional group tolerance. 相似文献
12.
Sandra Hübner Haijun Jiao Dr. Dirk Michalik Dr. Helfried Neumann Dr. Stefan Klaus Dirk Strübing Dr. Anke Spannenberg Dr. Matthias Beller Prof. Dr. 《化学:亚洲杂志》2007,2(6):720-733
Chiral N‐dienyl lactams are crucial building blocks for the synthesis of complex organic compounds. However, their generation is rather challenging. This paper reports on a highly efficient and diastereoselective multicomponent methodology utilizing chiral a mides, a ldehydes, and d ienophiles (AAD reaction). The three components readily react under in situ generation of chiral N‐dienyl lactams which undergo a subsequent Diels–Alder reaction. Different chiral amides have been employed in the standard protocol delivering yields up to 94 %, and selectivities up to 90 % de. Moreover, DFT calculations were performed to explain the obtained selectivities. 相似文献
13.
Braga AL Lüdtke DS Vargas F Paixão MW 《Chemical communications (Cambridge, England)》2005,(19):2512-2514
The catalytic enantioselective arylation of several aldehydes using boronic acids as the source of transferable aryl groups is described; the reaction is found to proceed in excellent yields and high enantioselectivities (up to 97% ee) in the presence of a chiral amino alcohol. 相似文献
14.
《Journal of molecular catalysis. A, Chemical》2007,261(1):120-124
The catalytic enantioselective arylation of several aldehydes using arylboronic acids as the source of transferable aryl groups is described; the reaction is found to proceed in excellent yields and high enantioselectivities (up to 96% ee) in the presence of a chiral amino alcohol derived from ephedrines and congeners. 相似文献
15.
Yu Lu Yudao Ma Shaobo Yang Manyuan Ma Hongju Chu Chun Song 《Tetrahedron: Asymmetry》2013,24(18):1082-1088
Several novel [2.2]paracyclophane-based amino thioureas have been designed and synthesized. The [2.2]paracyclophane-based amino thioureas were used as bifunctional catalysts for organocatalytic enantioselective aldol reactions between ketones and isatins, affording the desired adducts containing a chiral tertiary alcohol in high yields (up to 92% yield) and with good enantioselectivity (up to 88% ee). This is a successful example of employing planar chiral [2.2]paracyclophane-based amino thioureas in asymmetric aldol reactions. 相似文献
16.
The catalytic asymmetric Henry reaction of nitromethane to various aldehydes has been developed using a chiral binaphthylazepine derived amino alcohol and Cu(OAc)2·H2O as the catalyst. High yields and good enantioselectivities (up to 97% ee) were obtained for both aromatic and aliphatic aldehydes. Moreover, this catalytic system also works well for the diastereoselective Henry reaction to afford the corresponding adducts in up to 95:5 syn/anti selectivity and 95% enantioselectivity. 相似文献
17.
The paper describes stereoselective radical aryl migration reactions from sulfur in sulfonates to aryl radicals for the synthesis of axially chiral biaryls. A chirality center in secondary benzylic sulfonates is used to diastereoselectively (atroposelectively) install a stereogenic axis via a 1,5 aryl migration reaction. Atroposelectivity has not been investigated in stereoselective radical chemistry before. Good yields (53-82%) but low selectivities (up to 2 to 1) were obtained. 相似文献
18.
De-qiang Ran Tian-hua Shen Xiao-cong Zhou Jun-qi Li Fu-na Cui Chun-an Ma Qing-bao Song 《Russian Journal of Organic Chemistry》2013,49(6):849-852
Four chiral Schiff bases were synthesized conveniently from chiral amino alcohol and 2-hydroxynaphthalene-1-carbaldehyde. These ligands were used to catalyze the addition of nitroalkanes to aldehydes under ambient conditions in good yields with up to 91% ee. 相似文献
19.
Herein we report the synthesis of a chiral imidazolium salt derived from trans-L-hydroxyproline and its applications as a catalyst for the asymmetric aldol reaction. By performing the aldol reaction in [Bmim]NTf(2) as a solvent, we report excellent isolated yields of the aldol product (up to 99%), as well as modest to excellent selectivities (dr superior to 99:1. ee up to 89%). Mechanistic insights and the origins of the selectivity of the aldol reaction are discussed on the basis of the results obtained with two catalytic imidazolium salts having different H-bonding potential. 相似文献
20.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(12):3295-3299
Carbophilic gold carbenes generated from the decomposition of α‐diazoesters show high reactivity towards enamides, leading to an unprecedented aza‐ene‐type reaction. The presence of 0.1 mol % of a chiral Brønsted acid co‐catalyst is sufficient to give synthetically relevant γ‐keto esters in excellent yields and selectivities (up to 99 % yield, 97 % ee ). 相似文献