共查询到20条相似文献,搜索用时 675 毫秒
1.
2.
报道了甲酸/三乙胺体系中,(S,S) -TsDPEN-Ru络合物催化的不对称氧转移反应合成(S)-γ-胺基醇的方法.考察了不同底物的反应性能,β-单/二烷基胺基-2-噻吩酮在该还原体系中氧解得到1-(2-噻吩基)-1-丙酮;氮原子上吸电子基取代的底物以高收率、高立体选择性(>95%e.e.)得到还原产物.将这一反应用于... 相似文献
3.
The in situ catalysts prepared from [Rh(Cod)Cl]2 (Cod = 1,5-cyclooctadiene) and chiral alkylphenanthroline ligands 1–6 display a remarkable activity in the asymmetric hydrosilylation of acetophenone affording, after hydrolysis, the expected 1-phenylethanol in high yield and complete selectivity. High enantioselectivities, up to 76%, were obtained in the presence of 2-substituted derivatives 5 and 6, whereas 3-alkylphenanthrolines 1–4 gave e.e.'s not higher than 6%. High chemical yields, but modest enantioselectivities (10–20% e.e.) were recorded with the potentially terdentate ligands 7–10. Chiral alkylphenanthrolines were poorly efficient ligands in the asymmetric Ni-catalysed cross-coupling of -methylbenzylmagnesium chloride with vinyl bromide. 相似文献
4.
In recent years, many optically active β-amino alcohols, mostly derived from naturally occurring α-amino acids, have been incorporated into the asymmetric synthesis as chiral auxiliaries or ligands.1 An effective asymmetric catalysts, the oxazaborolidine-borane reagents, which were originally pioneered by Itsuno and Corey,2 were generally prepared from chiral β-amino alcohols by the reaction with boric acid or formed in situ in the presence of borane. These reagents provide excellent enanti… 相似文献
5.
GONG Da-chun ZHOU Hua WEI Ping OUYANG Ping-kai 《高等学校化学研究》2007,23(5):544-548
New ligand 1,2-bis{di[(R,R)-1,3,2-oxzaphosphlidine]phosphino}ethane [(R,R)-BDOPPEs 1,2,3 and 4] with C2-symmetric axis and bearing nitrogen and oxygen were synthesized from readily available optically active amino alcohols.Rh complexes with these ligands were highly enantioselective catalysts for asymmetric hydrogenation of N-benzoyldehydroamino acid derivatives and α-functionalized ketones in 99%e.e.and 98%e.e.,respectively.This new class of(R,R)-BDOPPEs 1,2,3 and 4 gave much more effectivity and enantionselectivity than their corresponding non-C2-asymmetric aminophosphine phosphinite. 相似文献
6.
WeiHuaHAN HaoRanLI 《中国化学快报》2005,16(1):15-16
(-)-cis-1, 3-Dibenzyl-hexahydrofuro[3, 4-d]imidazole-2, 4-dione was prepared by a new synthesis method from meso dicarboxylic acid and dehydroabietylamine by asymmetric reduction in good yield with up to 91.6% e.e. value. 相似文献
7.
Tsutomu Takeichi Motoji Arihara Michihiro Ishimori Teiji Ttsuruta 《Tetrahedron》1980,36(23):3391-3398
Optically active chloromethyloxirane was obtained from 1,3-dichloro-2-propanol by a process of asymmetric synthesis. The highest enantiomenc excess (e. e. ) of chloromethyloxirane that could be obtained was 67%, using Co(II) (3,5-Cl,Cl-sal)2(S-CHXDA) and K2CO3 as the catalyst and base, respectively. For purpose of comparison, asymmetric cyclizations of racemic 2,3-dichloro-1-propanol and 2-chloro-1-propanol were examined; optically active chloromethyloxirane and methyloxirane were obtained according to kinetic resolution mechanisms, although the optical purities of oxiranes formed were not so high. The mechanisms for the asymmetric reactions were investigated by circular dichroism and absorption spectroscopies. It was found that the cobalt (salen) type complex forms a new complex with alkali metal carbonate, similarly to the function of crown ether. The substrate interacts with the newly formed chiral complex, followed by cylization to give optically active oxiranes. 相似文献
8.
Asymmetric autocatalysis of 5-carbamoyl-3-pyridyl alkanols with amplification of enantiomeric excess
《Tetrahedron: Asymmetry》2000,11(21):4249-4253
5-Carbamoyl-3-pyridyl alkanols with low e.e. act as asymmetric autocatalysts in the consecutive asymmetric autocatalytic addition of diisopropylzinc to 5-carbamoyl-3-pyridinecarbaldehydes. The e.e. of pyridyl alkanol amplified up to 88% e.e. without the need for any other chiral auxiliary. 相似文献
9.
前手性酮的对映选择性还原在不对称合成中占有极其重要的地位。人们对这类反应进行了广泛的研究,其中Itsuno和Cory等发现的用手性硼杂口恶唑烷催化不对称还原的方法,已成为高对映选择性还原羰基化合物最成功的方法之一[1,2]。近年来,国内外许多文献报道... 相似文献
10.
Yu. N. Belokon' K. A. Kochetkov T. D. Churkina N. S. Ikonnikov S. A. Orlova N. A. Kuz'mina D. E. Bodrov 《Russian Chemical Bulletin》1993,42(9):1525-1529
The asymmetric Michael addition of methyl nitroacetate to crotonaldehyde catalyzed by chiral amines was carried out. The maximum chemical yield of diastereomeric products amounted to 95 %. The best asymmetric induction (42 % e.e.) was achieved in the case of catalysis by (S)-prolinol. The diastereomeric mixture was converted to a mixture of stereoisomeric 3-methyl-2-methoxycarbonylpyrrolidines. Absolute configurations of (2S,3S)-and (2R,3S)-isomers formed in excess were determined using GLC by comparison with authentic samples of racemic and optically pure forms of 3-methylproline.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1591–1595, September, 1993. 相似文献
11.
《Tetrahedron: Asymmetry》2001,12(22):3139-3145
A series of 2-oxoalkanephosphonates 2 were screened for reduction with Geotrichum candidum. Only diethyl 2-oxopropanephosphonate 2a underwent asymmetric reduction to give (+)-(R)-diethyl 2-hydroxypropanephosphonate 3a with 98% e.e. In turn, a series of racemic 2-hydroxyalkanephosphonates 3 were acetylated under kinetic resolution conditions in the presence of various lipases to give the corresponding 2-acetoxyalkanephosphonates 4 and recovered alcohols 3 in good yields and with e.e. up to 93%. 相似文献
12.
以金鸡纳碱衍生物作为手性修饰剂,研究了三苯基膦稳定的1.0%Ru+0.2%Rh/γ-Al2O3催化剂催化芳香酮多相不对称加氢,考察了修饰剂种类及浓度、碱添加剂种类及浓度、溶剂、氢气压力等因素对不对称加氢反应的影响.结果表明,金鸡纳碱衍生物对1.0%Ru+0.2%Rh/γ-Al2O3-tpp催化剂具有较好的修饰作用,在优化反应条件下苯乙酮加氢反应的对映选择性高达84%. 相似文献
13.
Catalytic Enantioselective and Regioselective [3+3] Cycloadditions Using 2‐Indolylmethanols as 3 C Building Blocks
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xiao‐Xue Sun Hong‐Hao Zhang Guo‐Hao Li Ying‐Ying He Prof. Dr. Feng Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(49):17526-17532
The first catalytic asymmetric cycloaddition using 2‐indolylmethanols as 3C building blocks has been established by a chiral phosphoric acid‐catalyzed enantioselective and regioselective [3+3] cycloaddition of 2‐indolylmethanols with azomethine ylides, which constructed biologically important tetrahydro‐γ‐carboline frameworks in high yields and excellent enantioselectivities (up to 83 % yield, 99:1 e.r.). This reaction not only represents the first application of 2‐indolylmethanols as 3C building blocks in catalytic asymmetric cycloadditions, but also has established an abnormal regioselectivity in indolylmethanol‐involved transformations. 相似文献
14.
15.
Xin-Qi Zhu Ze-Shu Wang Bo-Shang Hou Hao-Wen Zhang Prof. Dr. Chao Deng Prof. Dr. Long-Wu Ye 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(4):1683-1690
6π electrocyclization has attracted interest in organic synthesis because of its high stereospecificity and atom economy in the construction of versatile 5–7-membered cycles. However, examples of asymmetric 6π electrocyclization are quite scarce, and have to rely on the use of chiral organocatalysts, and been limited to pentadienyl-anion- and triene-type 6π electrocyclizations. Described herein is a zinc-catalyzed formal [4+3] annulation of isoxazoles with 3-en-1-ynol ethers via 6π electrocyclization, leading to the site-selective synthesis of functionalized 2H-azepines and 4H-azepines in good to excellent yields with broad substrate scope. Moreover, this strategy has also been used to produce chiral 2H-azepines with high enantioselectivities (up to 97:3 e.r.). This protocol not only is the first asymmetric heptatrienyl-cation-type 6π electrocyclization, but also is the first asymmetric reaction of isoxazoles with alkynes and the first asymmetric catalysis based on ynol ethers. 相似文献
16.
手性膦酸二酯类化合物的合成与结构 总被引:3,自引:0,他引:3
手性呋喃酮1a1b与亚磷酸三酯2a2b通过串联的不对称Michael加成/分子内Michalis-Arbazov重排反应,得到含磷官能团的新手性化合物5-(S)-(1S)-冰片氧基-4-膦酸二酯基-3-卤素-2(5H)-呋喃酮(3a~3d).该反应具有条件温和,产率高(69%~93%),光学纯度单一(d.e.≥98%)等特点.通过元素分析,IR,UV1HNMR13CNMR,MS,[α]D20等分析数据以及X射线四圆衍射确定了它们的化学结构和绝对构型. 相似文献
17.
Novel methods for the facile construction of 3,3-disubstituted and 3, 3-spiro 2H,4H-benzo[e][1,2]thiazine-1,1-diones 8a-h are described. o-Methyl lithiation of N-Boc-o-toluenesulfonamide 6 followed by reaction with a variety of ketones gave the corresponding carbinol sulfonamides 7a-g, which underwent cyclization under acidic (methanesulfonic acid) or neutral (NaI/TMSCl/MeCN) conditions to afford the sultams 8a-h in high yields. The chiral spiro sultams 8g, h were subjected to FClO(3) fluorination to give the N-fluorosultams 11a,b, respectively, which were tested for electrophilic asymmetric fluorination of aryl ketone enolates. As a result, the N-fluorosultam 11a exhibited modest asymmetric inducing abilities with the highest ee, reaching 70% for enantioselective fluorination of the lithium enolate of 2-methyl-1-tetralone. 相似文献
18.
Xin‐Qi Zhu Ze‐Shu Wang Bo‐Shang Hou Hao‐Wen Zhang Chao Deng Long‐Wu Ye 《Angewandte Chemie (International ed. in English)》2020,59(4):1666-1673
6π electrocyclization has attracted interest in organic synthesis because of its high stereospecificity and atom economy in the construction of versatile 5–7‐membered cycles. However, examples of asymmetric 6π electrocyclization are quite scarce, and have to rely on the use of chiral organocatalysts, and been limited to pentadienyl‐anion‐ and triene‐type 6π electrocyclizations. Described herein is a zinc‐catalyzed formal [4+3] annulation of isoxazoles with 3‐en‐1‐ynol ethers via 6π electrocyclization, leading to the site‐selective synthesis of functionalized 2H‐azepines and 4H‐azepines in good to excellent yields with broad substrate scope. Moreover, this strategy has also been used to produce chiral 2H‐azepines with high enantioselectivities (up to 97:3 e.r.). This protocol not only is the first asymmetric heptatrienyl‐cation‐type 6π electrocyclization, but also is the first asymmetric reaction of isoxazoles with alkynes and the first asymmetric catalysis based on ynol ethers. 相似文献
19.
Asymmetric reduction of aromatic ketones, with the reagent (1) prepared from borane-methyl sulfide (EMS) and (15, 25)-(+)-2-amino-3-methoxy-1-phenyl-1-propanol (3a) yielded the corresponding alcohols in 30–65% e.e. This reagent (1) is also effective for the asymmetric hydroboration of 2-phenyl-1-alkenes, isoelectronically similar to the aromatic ketones, and yielded the corresponding alcohols in 8–37% e.e. 相似文献