N-方酰麻黄碱配体的合成及催化前手性芳酮的不对称还原反应

方酸与醇反应成方酸二酯,后者与天然麻黄碱反应得到N-方酰麻黄碱或N-方酰双麻黄碱。单N-方酰麻黄碱与脂肪胺及硫氢化钠等反应合成了C-3位含氮和含硫的系列配体。首次将这些方酰麻黄碱配体经原位制备手性恶唑硼烷催化前手性芳酮及二酮的不对称还原反应,得到化学产率和e.e.值分别为85%-98%和52.5%-87.4%的手性仲醇。新化合物的结构已IR,^1H NMR,MS和元素分析所证实,化合物4b的晶体结构用X射线射确认。     

面包酵母催化不对称还原2,5-己二酮

选用10种面包酵母,研究其对2,5-己二酮的不对称还原特性。筛选出一种酵母S.c No.6,对底物2,5-己二酮有较高的转化活性和对映体选择性。初始底物浓度20 mmol.L-1,经酵母转化48h,2,5-己二醇得率为84.0%,e.e.值94.8%。采用气相色谱-质谱联用技术确认酵母培养液中存在中间产物5-羟基-2-己酮,并推测酵母不对称还原2,5-己二酮的反应分两步进行,首先生成中间产物(S)-5-羟基-2-己酮,而后二次加氢生成(2S,5S)-2,5-己二醇。     

手性质子酸催化酮的不对称直接α-烷基化反应研究

在有机合成中,羰基化合物的α-烷基化反应是一种重要的碳碳键形成策略.羰基化合物的不对称α-烷基化反应已经有较多的研究报道,但是,在已有的报道中多是使用脂肪醛作为烷基化反应的给体和手性胺作为催化剂.手性胺催化脂肪酮的不对称α-烷基化反应其立体选择性不是十分理想.西南大学化学化工     

新型小茴香酮双腙化合物的合成研究

以小茴香酮和水合肼为原料合成小茴香酮单腙(1),然后与芳香醛、脂肪酮等发生缩合反应合成一系列新型小茴香酮双腙(2a～2m)。探讨了不对称双腙类化合物的合成方法,并对所合成的产物通过IR、~1H NMR、~(13)C NMR和MS进行了鉴定和表征。     

新型手性方酸衍生物的合成及催化前手性芳酮的不对称 还原反应

方酸经酯化后与手性氨基醇反应,继而与脂肪胺、硫醇等作用,首次合成了11个新型手性方酰氨基醇配体。研究了它们经原位制成手性恶唑硼烷催化前手性芳酮的不对称还原的性能,得到手性仲醇的化学产率和e.e值分别为88%～98%和42%～81%。新化合物的结构经IR,1^HNMR,MS及元素分析证实,4b的绝对构型经X射线衍射确认。     

铑(I)催化的不对称硅氢化反应合成手性2-氨基-1-芳基乙醇研究

报道了以Rh()-手性2-(2-吡啶基)-4-羧甲基-1,3-噻唑烷为催化剂,2-氨基芳香酮的不对称硅氢化反应,在常温常压下手性2-氨基-1-芳基乙醇的产率几乎可达定量,产品光学纯度可达80%e.e以上.     

铑(Ⅰ)催化的不对称硅氢化反应合成手性2-氨基-1-芳基乙醇研究

报道了以Rh(I)－手性2－（2－吡啶基）－4－羧甲基－1，3－噻唑烷为催化剂，2－氨基芳香酮的不对称硅氢化反应，在常温常压下手性2－氨基－1－芳基乙醇的产率几乎可达定量，产品光学纯度可达80％e.e以上。     

2-吡喃酮的催化不对称Diels-Alder反应研究进展

2-吡喃酮是一种含有共轭二烯的杂环化合物,它可以作为一种特殊的双烯体参与Diels-Alder反应.经过几十年的发展,2-吡喃酮的Diels-Alder反应在复杂天然产物的合成中得到了广泛地应用.近年来,2-吡喃酮的催化不对称Diels-Alder反应也引起了合成化学家的关注.对2-吡喃酮参与的不对称正电子需求和反电子需求的Diels-Alder反应的发展,以及它们在天然产物全合成中的应用进行了总结.     

金属Ir4 Cluster催化丙烯加氢反应势能面的密度泛函理论研究

用密度泛函理论(DFT)对金属Ir4 cluster催化丙烯Propene加氢反应的反应机理进行了理论研究. 在B3LYP理论水平下优化了反应通道上反应物、中间体、过渡态和产物各驻点物种的几何构型, 构建了该反应的基态势能面. 计算结果表明, Ir4 cluster催化丙烯加氢反应, 主要通过3条反应通道(c,d和e)进行. 主反应通道c 是H1原子先经过中间体1加成到丙烯的边端C上形成中间体3, 然后H2原子经过渡态TS3—5, 中间体5和过渡态TS5-P加成到中间C上生成产物P. c通道无论从动力学角度还是热力学角度都是最有利的; 反应通道d和e中的最高势垒和通道c上的相比差别不大, 具有一定的竞争性, 是次通道.     

有机催化靛红衍生酮亚胺与噁唑酮的不对称Mannich型加成反应

研究了手性磷酸催化的靛红衍生酮亚胺与噁唑酮的不对称Mannich型加成反应, 以良好至优秀的收率(高达97%)、 对映选择性(高达99% e.e.)以及非对映选择性(均>20∶1 d.r.)得到一系列含噁唑酮骨架的手性3,3′-二取代氧化吲哚化合物. 该反应可以进行扩大化和衍生反应.     

Catalytic enantioselective allylation of ketones via a chiral indium(III) complex

[reaction: see text] A chiral indium complex has been discovered to effect high enantioselectivities in the addition of allyltributylstannanes to ketones. The allylation of a variety of aromatic, alpha,beta-unsaturated and aliphatic ketones resulted in good yields and high enantioselectivities (up to 92% ee).     

Highly Enantioselective Aldol Reactions between Acetaldehyde and Activated Acyclic Ketones Catalyzed by Chiral Primary Amines

Highly enantioselective cross‐aldol reactions between acetaldehyde and activated acyclic ketones are reported for the first time. Various acyclic ketones, such as saturated and unsaturated keto esters, reacted with acetaldehyde in the presence of a chiral primary amine and a Brønsted acid to afford optically enriched tertiary alcohols in good yields and with excellent enantioselectivities. Trifluoromethyl ketones were tolerable under the reaction conditions, thereby affording the trifluoromethyl carbinol in good‐to‐excellent yields and enantioselectivities. Structural modification of the chiral amines from the same chiral source switched the stereoselectivity of the products. The utility of aldol chemistry was demonstrated in the brief synthesis of functionally enriched δ‐lactones. Theoretical calculations on the transition‐state structure indicated that the protonated tertiary amine could effectively activate the carbonyl group of a keto ester to promote the addition process through hydrogen‐bonding interaction and, simultaneously, provide an appropriate attacking pattern for the approach of the keto ester to the enamine, which is formed from acetaldehyde and the chiral catalyst, on a particular face, resulting in high enantioselectivity.     

Highly active chiral phosphoramide-Zn(II) complexes as conjugate acid-base catalysts for enantioselective organozinc addition to ketones

A highly efficient enantioselective organozinc (R2Zn) addition to ketones catalyzed by chiral phosphoramide-Zn(II) complexes (1-10 mol %) has been developed. These complexes serve as conjugate Lewis acid-Lewis base catalysts. Chiral phosphoramides are derived from an inexpensive natural amino acid (i.e., L-valine). From a variety of nonactivated aromatic and aliphatic ketones, the corresponding optically active tertiary alcohols were obtained in high yields with high enantioselectivities (up to 98% ee) under the mild reaction conditions.     

Study of the lanthanide-catalyzed, aqueous, asymmetric Mukaiyama aldol reaction

The development of efficient methods for the asymmetric Mukaiyama aldol reaction in aqueous solution has received great attention. We have developed a new series of chiral lanthanide-containing complexes that produce Mukaiyama aldol products with outstanding enantioselectivities. In this paper, we describe an optimized ligand synthesis, trends in stereoselectivity that result from changing lanthanide ions, and an exploration of substrate scope that includes aromatic and aliphatic aldehydes and silyl enol ethers derived from aromatic and aliphatic ketones.     

Direct enantioselective Michael addition of aldehydes to vinyl ketones catalyzed by chiral amines

Chiral amines such as (S)-2-[bis(3,5-dimethylphenyl)methyl]pyrrolidine and the C(2)-symmetric (2S,5S)-2,5-diphenylpyrrolidine can catalyze the direct enantioselective Michael addition of simple aldehydes to vinyl ketones. The conditions for this organocatalytic reaction have been optimized and it has been found that the chiral amines catalyze the formation of optically active substituted 5-keto aldehydes in good yields and enantioselectivities, using aldehydes and, e.g., methyl vinyl ketone as starting compounds. Taking into account that the chiral amine can activate the aldehyde and/or the enone, the mechanism for the reaction has been investigated. On the basis of intermediate synthesis, nonlinear effect, and theoretical investigations, the mechanism for the catalytic direct enantioselective Michael addition of aldehydes to vinyl ketones is discussed.     

C−N Axial Chiral Hypervalent Iodine Reagents: Catalytic Stereoselective α-Oxytosylation of Ketones

A simple synthesis of a library of novel C−N axially chiral iodoarenes is achieved in a three-step synthesis from commercially available aniline derivatives. C−N axial chiral iodine reagents are rarely investigated in the hypervalent iodine arena. The potential of the novel chiral iodoarenes as organocatalysts for stereoselective oxidative transformations is assessed using the well explored, but challenging stereoselective α-oxytosylation of ketones. All investigated reagents catalyse the stereoselective oxidation of propiophenone to the corresponding chiral α-oxytosylated products with good stereochemical control. Using the optimised reaction conditions a wide range of products was obtained in generally good to excellent yields and with good enantioselectivities.     

Catalytic, enantioselective aldol additions to ketones

Catalytic, enantioselective additions of a trichlorosilyl ketene acetal to ketones have been demonstrated. The trichlorosilyl enolate of methyl acetate undergoes a rapid and high-yielding aldol addition to a wide range of ketones (aromatic, olefinic, acetylenic, aliphatic) in the presence of a catalytic amount of pyridine N-oxide. Moreover, in the presence of a catalytic amount (10 mol %) of a chiral bispyridine bis N-oxide (possessing both axial and central chiral elements) the aldol addition takes place again in excellent yield and with good stereoselectivity. The enantioselectivities of the additions are highly variable (7-86% ee) and are strongly dependent on the structure of the ketone acceptor. Aromatic methyl ketones gave the highest selectivity, whereas olefinic ketones were the least selective.     

Catalytic Enantioselective Conjugate Alkynylation of α,β‐Unsaturated 1,1,1‐Trifluoromethyl Ketones with Terminal Alkynes

The first catalytic enantioselective conjugate alkynylation of α,β‐unsaturated 1,1,1‐trifluoromethyl ketones has been carried out. Terminal alkynes and 1,3‐diynes were treated with trifluoromethyl ketones in the presence of a low catalytic load of a Cu^I‐MeOBIPHEP complex (2.5 mol %) and triethylamine (10 mol %) to give the corresponding trifluoromethyl ketones bearing a propargylic stereogenic center at the β position with good yields and excellent enantiomeric excesses in most of the cases. No 1,2‐addition products were formed under the reaction conditions. The procedure showed broad substrate scope for alkyne, diyne, and enone. A rationale for the observed stereochemistry has been provided. Finally, the potential application of the reaction products in the synthesis of chiral tetrahydrofurans bearing a trifluoromethylated quaternary stereocenter has been devised.     

Enantioselective Direct Alkynylation of Ketones Catalyzed by Chiral CCN Pincer RhIII Complexes

A direct asymmetric alkynylation of ketones with new chiral CCN Rh catalysts containing N‐heterocyclic carbene and oxazoline hybrid ligands is described. The catalytic reaction of fluoroalkyl‐substituted ketones, ArCOCF₂X (X=F, Cl, H), with aromatic and aliphatic alkynes yielded the corresponding chiral propargyl alcohols with high enantioselectivity. Control and kinetic experiments suggested a bis(alkynyl) Rh intermediate as the active species for the C?C bond‐forming step.     

Lewis Base Organocatalyzed Enantioselective Hydrosilylation of α-Keto Ketimines

A chiral Lewis base organocatalyzed enantioselective hydrosilylation ofa-keto ketimines was investigated.The reactions afforded various enantioenriched a-amino ketones with good yields（up to 95％） in moderate to good enantioselectivities（up to 98％ e.e.）.Furthermore,one of the products was reduced to a chiral 1,2-amino alcohol.Following cyclization of it with triphosgene generated a cannabinoid receptor 1 （CB 1） inhibitor with good diastereoselectivity.