Catalytic Asymmetric Dearomatization of Indolyl Dihydropyridines through an Enamine Isomerization/Spirocyclization/Transfer Hydrogenation Sequence

A highly efficient synthesis of enantioenriched spiroindolines by catalytic asymmetric dearomatization of indolyl dihydropyridines through a chiral phosphoric acid catalyzed enamine isomerization/spirocyclization/transfer hydrogenation sequence has been developed. This reaction proceeds under mild reaction conditions, affording novel spiroindolines in good yields (up to 88 %) with excellent enantioselectivity (up to 97 % ee). DFT calculations provide insights into the reaction mechanism as well as the origin of stereochemistry.     

一类新型手性烷基氨基酚类配体的合成

利用Mannich反应, 高对映选择性地以中等产率合成了三个新型烷基氨基苯酚类配体及6个具有C₂对称轴的烷基氨基萘酚类配体. 合成的9个新化合物的结构经元素分析, IR, ¹H NMR, ¹³C NMR和MS等确定, 其中两个化合物4和7通过X射线单晶衍射确定了新生成的手性中心的绝对构型.     

Stereoselectivity of 1,3-dipolar cycloadditions of l-valine-derived nitrones with methyl acrylate

Chiral nitrones derived from l-valine react with methyl acrylate to afford the corresponding diastereomeric 3,5-disubstituted isoxazolidines. The dibenzylsubstituted nitrone gave also 3,4-disubstituted isoxazolidine in 4% yield, additionally. The stereoselectivity was dependent on the steric hindrance of the nitrone and reaction conditions. High pressure decreased the reaction time of the cycloadditions. The major products were found to have the C-3/C-6 erythro and C-3/C-5 trans relative configuration. The major cycloadduct undergoes N-O cleavage and deprotection to a chiral diaminodiol derivative.     

酸催化的二芳基甲醇脱水环化氧化芳构化直接构筑4-芳基喹啉

我们发展了酸催化的二芳基甲醇的脱水环化氧化芳构化的方法,直接高产率（高达81%）的合成轴手性的4-芳基喹啉.而且,Lewis酸Zn（OTf）₂和手性膦酸都能催化这个反应,初步的不对称研究可以用er 71：29得到产物.     

联苯二甲酸类手性分子钳的微波合成

在微波辐射条件下, 以联苯二甲酸为间隔基, L-氨基酸甲酯为手臂, 合成了7个新型手性分子钳. 其结构经¹H NMR, IR, MS和元素分析所证实. 与常规加热的一般合成方法相比, 该法明显地提高了反应速度和产率. 初步的实验结果表明, 这类分子钳人工受体对D/L-氨基酸甲酯具有良好的对映选择性识别性能.     

Cooperative Ni/Cu-Catalyzed Asymmetric Propargylic Alkylation of Aldimine Esters

A novel Ni/Cu dual catalysis gives rise to fundamentally new cooperative reactivity and enables the regio- and enantioselective propargylic alkylation reaction. A diverse set of α-quaternary propargylated amino ester derivatives were synthesized in good yields with excellent enantioselectivity (up to 99 % ee). This work highlights the power of cooperative catalysis, which can be expected to have broad implications in homogeneous catalysis beyond the highly valuable synthetic intermediates.     

新型手性硫醚-亚磷酰胺配体的设计与应用

根据模块组合法原理,设计并合成了一种具有亚磷酰胺结构的硫醚配体,该配体具有原料便宜易得、合成步骤简单、易于修饰和结构稳定等特点。以配体/钯络合物催化的丙二酸二甲酯与1,3-二苯基烯丙基醋酸酯的烯丙基化反应作为模板反应,探究了溶剂、碱对其立体控制的影响。随后探究了中心手性与轴手性的匹配/错配现象以及硫醚片段的空间位阻、电性对反应立体控制的作用。在最佳条件下,产物的对映选择性能够达到-76% ee。     

RuCl2(BISBI)[(R,R)-DPEN]催化苯乙酮不对称加氢反应研究

报道了配合物RuCl₂(BISBI)[(R,R)-DPEN] [BISBI＝2,2'-二(二苯膦亚甲基)-1,1'-联苯, DPEN＝1,2-二苯基乙二胺]的合成和表征, 并研究了其在苯乙酮不对称加氢反应中的催化性能. 考察了底物/催化剂物质的量比、碱浓度、反应温度和氢气压力等对催化活性和对映选择性的影响, 在苯乙酮/KOH/催化剂的物质的量比为30000∶250∶1, 氢气压力为2 MPa, 反应温度为35 ℃时, 苯乙酮的转化率和生成α-苯乙醇的对映选择性分别达到了100%和65% ee.     

Palladium-Catalyzed Cascade C−H Functionalization/Asymmetric Allylation Reaction of Aryl α-Diazoamides and Allenes: Lewis Acid Makes a Difference

A Pd-catalyzed cascade C−H functionalization/asymmetric allylation reaction with aryl α-diazoamides and allenes has been developed. The reaction provides an efficient approach to construct chiral 3,3-disubstituted oxindole derivatives in high levels of yield and enantioselectivity (up to 93 % ee). Notably, the chromium complex works as Lewis acid to facilitate the formation of palladium carbene and to enhance acidity of carboxylic acid, allowing for higher stereochemical control and efficiency.     

Cooperative Ni/Cu‐Catalyzed Asymmetric Propargylic Alkylation of Aldimine Esters

A novel Ni/Cu dual catalysis gives rise to fundamentally new cooperative reactivity and enables the regio‐ and enantioselective propargylic alkylation reaction. A diverse set of α‐quaternary propargylated amino ester derivatives were synthesized in good yields with excellent enantioselectivity (up to 99 % ee). This work highlights the power of cooperative catalysis, which can be expected to have broad implications in homogeneous catalysis beyond the highly valuable synthetic intermediates.     

Preparation and properties of ZnO nanorod array/liquid crystal composite system

ABSTRACT

In this study, By hydrothermal reaction, we prepared ZnO nanorod array of high aspect ratio with different growth time. The prepared ZnO nanorod array was on one side of the liquid crystal cell, the another side of the liquid crystal cell is ITO-glass, then the ZnO nanorod array/liquid crystal composite was injected into the liquid crystal cell. Experimental results showed that the bandwidth of the reflection spectrum of the ZnO nanorod array/liquid crystal composite system was wider than the system without ZnO nanorod array. In addition, effects of polymerisation temperatures and the length of ZnO nanorod array on the broad-band reflection of N*-LC composite films were systematically investigated.     

1-乙基-3-甲基咪唑L-乳酸盐作为手性配体用于氨基酸的手性拆分

基于手性配体交换机理,研究了以手性离子液体1-乙基-3-甲基咪唑L-乳酸盐([EMIM][L-Lac])为手性配体拆分色氨酸对映体(Trys)、苯丙氨酸对映体(Phes)和酪氨酸对映体(Tyrs)的方法。实验考察了背景电解质和中心离子种类、手性配体与中心离子的浓度及比例、运行缓冲液pH等因素对Trys、Phes和Tyrs手性拆分的影响。研究发现,当运行缓冲液为40.0 mmol/L [EMIM][L-Lac]、20.0 mmol/L氯化铜(pH 4.5)时,3对对映体均能得到良好的手性拆分。为了验证[EMIM][L-Lac]的良好性能,实验进一步将L-乳酸(L-Lac)作为手性配体用于Trys的手性拆分。对比实验发现,单独使用L-乳酸,DL-Try只能得到部分拆分,加入离子液体1-乙基-3-甲基咪唑醋酸盐(EMIM-Ace)后,DL-Try分离情况得到了很大改善,但出峰时间延长至30 min以上。而使用[EMIM][L-Lac]时,Trys的出峰时间均在15 min以内。实验最后还对手性拆分机理做了进一步讨论。实验结果表明:在EMIM-Ace辅助L-Lac体系中,EMIM-Ace仅被用于抑制电渗流,并未参与手性配体交换反应;而在[EMIM][L-Lac]体系中,参与手性配体交换反应的主要是未解离的[EMIM][L-Lac],而不是解离后的L-乳酸根离子形成的L-乳酸。     

Enantioselective Reduction of Prochiral Ketones with NaBH4/Me2SO4/(S)-Me-CBS

The enantioselective reduction of prochiral ketones with NaBH₄/Me₂SO₄/(S)-Me-CBS is described. Borane is generated in situ via the reaction of NaBH₄ with Me₂SO₄ in tetrahydrofuran, which is as efficient as the commercial one. Such in situ–generated borane reagent was applied to reduce prochiral ketones in the presence of chiral oxazaborolidine catalyst directly. The corresponding chiral secondary alcohols were obtained with excellent enantiomeric excesses (93–99% ee) and good to excellent yield (80–99%).     

手性相转移催化剂及其在不对称催化反应中的应用

综述了手性季铵盐、手性冠醚以及其它新型手性相转移催化剂的制备及其在各种不对称相转移催化反应如烷基化反应、Michael加成反应、Aldol反应、Mannich反应、氧化反应及还原反应中应用的最新进展.     

The effect of chiral solvent and various kinds of chiral organic salts on the asymmetric hydrogenation of methyl acetoacetate over an improved tartaric acid modified Raney nickel catalyst

The influence of the chiral ionic liquid (CIL) on the asymmetric hydrogenation of methyl acetoacetate (MAA) over an improved tartaric acid-modified Raney nickel catalyst using it as reaction medium was investigated. At the same time, we also studied the effect of up to eight chiral ionic salts, and ionic liquids on this reaction using these ionic salts as co-catalyst. Although no obviously improved optical yields were gained, the possible cause has been given.     

Greatly Enhanced Fluorescence by Increasing the Structural Rigidity of an Imine: Enantioselective Recognition of 1,2‐Cyclohexanediamine by a Chiral Aldehyde

An aldehyde that is not fluorescent responsive toward a chiral diamine has been converted to a sensitive fluorescence enhancement sensor through incorporation of an additional hydrogen bonding unit to increase the structural rigidity of the reaction product of the aldehyde with the diamine. This new chiral aldehyde is synthesized in one step from the reaction of (S)‐3‐formylBINOL with salicyl chloride. When treated with trans‐1,2‐cyclohexanediamine in ethanol, it shows greatly enhanced fluorescence at λ=410 nm with good enantioselectivity. NMR and mass spectroscopic methods are used to investigate the reaction of the chiral aldehyde with the diamine. This study has revealed a two‐stage reaction mechanism including a fast imine formation and a slow ester cleavage.     

双中心协同催化作用在不对称合成中的应用

介绍了双中心协同催化作用的概念以及A型和B型两类催化剂。综述了A型催化 剂在不对称硝基－类羟醛反应、迈克尔加成反应、亚胺和醛的氢膦酰化反应、曼尼 希反应、不对称醛酮羟醛反应以及环氧开环反应中的应用；同时简要介绍了B型催 化剂在不对称合成中的应用。     

Chiral rare earth organophosphates as homogeneous Lewis acid catalysts for the highly enantioselective hetero-Diels–Alder reactions

Various trivalent rare earth-chiral phosphate complexes [(R)-1-RE, (R)-3-RE, and (R)-4-Ce] were prepared and evaluated as a Lewis acid catalyst for the asymmetric hetero-Diels–Alder reaction of aldehydes with the Danishefsky's diene. Some of them effectively promoted the reaction at room temperature in the presence or absence of achiral additives under homogeneous conditions to afford the corresponding cycloadducts with high ee's (up to 99% ee). During these reactions, remarkably high asymmetric amplifications (positive nonlinear effects) were observed as the first example in the metal ion–chiral ligand 1:3 catalytic system. A scandium catalyst bearing the H₈-BNP ligand, (R)-3-Sc, could be recovered after the reaction and successfully reused for the next round of reactions. In addition, the hetero-Diels–Alder reaction of -keto esters was effectively catalyzed by the ytterbium complex, (R)-1-Yb, without any additives thus producing the asymmetric quaternary carbon in excellent enantioselectivities (up to >99% ee).     

The synthesis of new chiral rhodium complexes and their crystal structures

Two novel chiral rhodium complexes were successfully synthesized from the reaction of chiral bidentate nitrogen ligands with RhCl₃·3H₂O in ethanol under reflux. Their unusual crystal structures were unambiguously obtained by X‐ray analysis. Copyright © 2001 John Wiley & Sons, Ltd.