Optically Active Sulfoxides and Low-Valent Titanium in Asymmetric Synthesis of Natural Products

The total synthesis of lasiodiplodin via optically active sulfoxides and the preparation of polyenes through low valent titanium reagents are described.     

One-Pot Vinylation of Secondary Phosphine Chalcogenides with Vinyl Sulfoxides

A facile, one-pot vinylation of secondary phosphine chalcogenides with alkyl(or aryl) vinyl sulfoxides has been elaborated. The vinylation comprises the nucleophilic addition of secondary phosphine chalcogenides to the vinyl sulfoxides (～50 mol% KOH, dioxane, 25–40°C, 1 h) followed by the elimination of sulfenic acids from the adducts (additional equivalent of KOH, 60–70°C, 1.5–2.0 h), the yields of target tertiary vinyl phosphine chalcogenides reaching 92%.     

手性亚砜在不对称合成中的应用

本文对手性亚砜的制备及其在不对称反应和天然产物合成中的应用进行了综述。     

Applications of Chiral Squaramides: From Asymmetric Organocatalysis to Biologically Active Compounds

This review seeks to provide coverage on the recent advances in chiral squaramide‐catalyzed asymmetric transformations and their applications in the synthesis of a variety of chiral biologically active compounds. It aims to give an overview highlighting the new reaction types and enantioenriched medicinal scaffolds developed in the last few years.

     

Catalytic, Asymmetric Cyclopropanation of Diphenylethene Mediated by Chiral Copper-(Schiff Base) Complexes

Asymmetric cyclopropanation of diphenylethene with diazoacetates was catalyzed by new copper-(Schiff base) complexes. The effects of the substituents in substituted salicylaldehyde on the ee's were studied, and a 94.5% ee was achieved. This revised version was published online in June 2006 with corrections to the Cover Date.     

Dimeric TADDOL Phosphoramidites in Asymmetric Catalysis: Domino Deracemization and Cyclopropanation of Sulfonium Ylides

A gold‐catalyzed asymmetric cyclopropanation of unactivated olefins with sulfonium ylides in the presence of a bimetallic catalyst with a novel dimeric TADDOL‐phosphoramidite ligand is reported. This transformation allows a rare gold‐catalyzed dynamic deracemization of chiral racemic substrates, where the same catalyst is responsible for several synergistic tasks in solution. The products are useful building blocks in synthesis and enable expeditious access to natural products.     

醇腈酶促不对称合成手性氰醇反应条件的研究

利用气相色谱手性分析,对醇腈酶促不对称合成手性氰醇中的pH值、温度、底物浓度和水含量对酶反应速度和非酶反应速度的影响作了研究。结果表明,上述因素对酶反应和非酶反应速度均有显著影响。在水含量较低的非水相酶反应体系中,pH值在4．0以下或反应温度为0－5℃时,非酶反应受到较大程度的抑制,而酶反应仍具有相对较快的反应速度,故可获得高光学纯度的产物。     

光学活性有机钛试剂与苯甲醛不对称加成反应

光学活性二醇（１Ｒ，２Ｒ）－（＋）－１，２－二苯基－１，２－乙二醇（Ⅲａ）和（２Ｒ，３Ｒ）－（－）－１，１，４，４－四苯基－２，３－（缩丙酮）－１，４－丁二醇（Ⅲｂ）分别修饰Ｔｉ（ＯＰｒｉ）３Ｃｌ，再与甲基锂和乙基锂进行烷基化，制备出新的手性有机钛试剂Ⅱａ和Ⅱｂ，然后与苯甲醛进行加成，所得１－苯基乙醇（Ⅳａ）和１－苯基丙醇（Ⅳｂ）的光学收率分别为２５～６５％ｅ．ｅ．和１０～２０％ｅ．ｅ．。简单讨论了Ｃ２－对称型二醇对立体选择性及反应条件的影响     

手性金属配合物催化的不对称环丙烷化反应的新进展

总结了近年来关于环丙烷化反应中各种手性金属催化剂的研究进展, 包括席夫碱、噁唑啉、卟啉、联吡啶及四吡啶、羧酸酯等类型的手性化合物作为配体的金属催化剂.     

壳聚糖希夫碱铜多相催化剂的制备及其催化苯乙烯环丙烷反应的研究

采用均相和多相两种方法合成了壳聚糖希夫碱－Cu(Ⅱ)配合物，用于催化苯乙烯的不对称环丙烷反应，考察了不同制备方法和不同铜含量对催化剂催化性能的影响以及催化剂的重复使用情况，当催化剂的铜含量为4．4％时，得到20．7％的ee值。     

新型手性双二茂铁希呋碱亚胺配体的合成及其在不对称环丙烷化反应中的应用

以手性二茂铁乙胺为手性前体分别与吡啶二醛和吡啶二酮进行希呋碱缩合反应，合成了两种二茂铁手性亚胺膦配体，并经元素分析，^1HNMR，^31PNMR等手段进行了表征，用这类化合物作为手性配体，研究了其金属Ru(Ⅱ)配合物对苯乙烯与重氮乙酸乙酯的不对称环丙烷反应的催化作用，结果表明该类化合物的Ru(Ⅱ)配合物具有很高的催化活性。     

Asymmetric Cyclopropanation Catalyzed by Four Stereoisomers of a Copper-(Schiff-base) Complex with Double Chiral Centers

Catalytic asymmetric cyclopropanation of diazoacetates with olefins has attracted much attention. Those catalysts containing various metals and optically active ligands have been employed for this reaction1,2. The first catalytic asymmetric cyclopropanation reaction was reported in 1966 by Nozaki et al.3. The author used the copper(II) complex 1 bearing a salicyladimine ligand as catalyst though with a low e.e. value of 6%. Aratani and his coworkers designed the copper-(Schiff-base) comp…     

手征性杂氮钛三环化合物的合成

杂氮钛三环(titatrane)(Ⅰ)是一类具有五配体特殊结构的杂环化合物,由于对其合成工作研究的不多,所以这类化合物的一些性质还鲜为人知。我们对杂氮钛三环的合成方法做了改进,将手性中心引入到这类化合物中,合成了下列结构图中(Ⅱ)所示的具有手性的杂氮钛三环。     

Asymmetric Sulfonium Ylide Mediated Cyclopropanation: Stereocontrolled Synthesis of (+)‐LY354740

The reaction of ester‐stabilized sulfonium ylides with cyclopentenone to give (+)‐ 5 ((1S,5R,6S)‐ethyl 2‐oxobicyclo[3.1.0]hexane‐6‐carboxylate), an important precursor to the pharmacologically important compound (+)‐LY354740, has been studied using chiral sulfides operating in both catalytic (sulfide, Cu(acac)₂, ethyl diazoacetate, 60 °C) and stoichiometric modes (sulfonium salt, base, room temperature). It was found that the reaction conditions employed had a major influence over both diastereo‐ and enantioselectivity. Under catalytic conditions, good enantioselectivity with low diastereoselectivity was observed, but under stoichiometric conditions low enantioselectivity with high diastereoselectivity was observed. When the stoichiometric reactions were conducted at high dilution, diastereoselectivity was reduced. This indicated that base‐mediated betaine equilibration was occurring (which is slow relative to ring closure at high dilution). Based on this model, conditions for achieving high enantioselectivity were established as follows: use of a preformed ylide, absence of base, hindered ester (to reduce ylide‐mediated betaine equilibration), and low concentration. Under these conditions high enantioselectivity (95 % ee) was achieved, albeit with low diastereocontrol. Our model for selectivity has been applied to other sulfonium ylide mediated cyclopropanation reactions and successfully accounts for the diastereoselectivity observed in all such reported reactions to date.     

5-羟基色胺受体激动剂(1R,2S)-(-)-2-(2-羟基苯基)-N,N-二丙基环丙胺的不对称合成

利用手性双唑啉与三氟甲磺酸亚铜催化2-甲氧基苯乙烯与重氮乙酸二环己基甲酯的不对称环丙烷化反应合成了手性环丙烷羧酸酯,用氢氧化钠对其进行选择性水解得到全反式环丙烷羧酸,其ee值经GC测定为88%.进一步经过Curtius重排、烷基化等反应及重结晶等步骤合成了光学纯的具有生理活性的环丙胺化合物1a和1b.     

Synthetic Approaches to Biologically Active C-2-Substituted Benzothiazoles

Numerous benzothiazole derivatives are used in organic synthesis, in various industrial and consumer products, and in drugs, with a wide spectrum of biological activity. As the properties of the benzothiazole moiety are strongly affected by the nature and position of substitutions, in this review, covering the literature from 2016, we focus on C-2-substituted benzothiazoles, including the methods of their synthesis, structural modification, reaction mechanisms, and possible pharmacological activity. The synthetic approaches to these heterocycles include both traditional multistep reactions and one-pot atom economy processes using green chemistry principles and easily available reagents. Special attention is paid to the methods of the thiazole ring closure and chemical modification by the introduction of pharmacophore groups.