平面手性化合物的绝对构型及其判定的教学方法

平面手性是手性的一种特殊情形。结合实例详细阐述了手柄化合物、环蕃化合物、反式环烯烃、轮烯类化合物、金属茂化合物等平面手性化合物的绝对构型及判定方法。     

手性化合物绝对构型确定的方法与应用

手性分子绝对构型(AC)的确定在手性化学研究与应用中至关重要.近年测定手性化合物AC的各种方法,根据其原理可主要分为三大类.第一类是在手性环境下激发手性化合物的原子核从而测定手性化合物AC的核磁共振(NMR)法,包括应用芳环抗磁屏蔽效应的NMR法和应用配糖位移效应的NMR法;第二类是基于原子共振散射的X射线衍射(XRD...     

一种标定手性轴化合物构型的简便方法

一、引言早在1908—1909年(英)Perkin Jr.Pope合成的旋光4-甲基环己亚基乙酸1被认为是第一个不含不对称碳原子的旋光化合物,改变了化学家们以前认为     

超分子凝胶:结构多样性与超分子手性

超分子凝胶作为一种重要的软物质材料,在构建多重刺激响应性、光电功能,以及生物相容材料等功能软物质方面表现出了独特的优越性。超分子凝胶在形成过程中往往得到比较均一的纳米结构,且具有结构多样性;而另一方面,超分子凝胶的构筑单元大部分是手性分子,超分子凝胶也是实现手性在超分子层次/纳米层次表达的重要途径,尤其是手性传递、手性放大、不对称催化方面,同时超分子凝胶也是构筑手性纳米结构的重要手段。本文主要对超分子凝胶形成中的纳米结构以及形貌的多样性和超分子手性进行介绍,并展望该领域未来的发展方向。     

手性酞菁的合成及其绝对构型

在锂存在的条件下在正戊醇中回流环化四聚相应的光学活性的前驱体联二萘[2,1-e:1',2'-g][1,4]二羟基-5,6-邻苯二氰, 然后用醋酸酸化处理, 合成了一对对映的四个联二萘酚基团取代的手性自由酞菁四(联二萘[1,2-e:1',2'-g]-1,4-二羟基)[2,3-b;2',3'-k;2',3'-t;2'',3''-c']酞菁(1), 并利用一系列的光谱学方法以及元素分析表征了这种新型的手性酞菁化合物. 单晶X衍射分析确定了两种对映体的绝对构型, 从而阐明了自由酞菁(1)的手性分配.     

手性溶剂诱导非手性物质手性的研究进展

手性溶剂诱导非手性物质产生手性是目前合成手性物质的主流方法之一。与传统的手性物质合成方法相比,手性溶剂诱导法不仅避免了使用昂贵的手性试剂,还能扩大合成手性物质的结构范围,具有潜在的应用前景。目前,手性溶剂诱导方法适用范围已经涵盖了有机小分子、低聚物和聚合物体系。本文主要对手性溶剂诱导方法发展的历史背景,手性溶剂诱导小分子及低聚物的手性,手性溶剂诱导非手性聚合物产生超分子手性,主要包括π-共轭聚合物和σ-共轭聚合物这几个方面展开了综述。     

手性化合物的命名

在总结各种手性化合物命名的基础上,加入了硅,氮,磷,硫,砷手性化合物的命名,着重阐述了新型手性分子的命名法则,并配以实例说明。     

手性杯芳烃及其超分子手性

杯芳烃是由苯酚单元通过亚甲基连接而成的空腔型分子,具有衍生位点多,构象丰富等特点,被称为第三代主体分子。在分子层次,依手性因素的结构特点不同,可将手性杯芳烃分为具有手性亚单元的杯芳烃、固有手性杯芳烃和桥手性杯芳烃。在超分子层次,杯芳烃自身或杯芳烃与其他分子或离子在溶液中、晶态中或二维表面可通过非共价键力形成多种拓扑结构的纳米手性聚集体。研究手性杯芳烃和基于杯芳烃的超分子手性组装体的合成、结构和性能,不仅在理解手性起源、手性结构等方面具有理论意义,而且有望获得以分子识别为基础的手性传感器、手性催化剂、手性分离材料、手性载体和手性纳米材料。本文综述近十年来有代表性的分子手性杯芳烃和以杯芳烃为组分的超分子手性聚集体的设计、合成、结构和功能。着重展示杯芳烃骨架在形成新颖分子手性和超分子手性上的优势,以及杯芳烃单元在实现特定功能如手性识别时发挥的作用。相信随着杯芳烃合成技术和杯芳烃超分子设计的发展,必将进一步发挥杯芳烃的结构优势,涌现出更多性能优异的手性杯芳烃功能分子和超分子手性杯芳烃功能材料。     

甲基取代的手性环酯化合物的螺旋结构与旋光性分析

利用螺旋片段判定规则,结合X射线衍射结构图及模型结构,对4个大环酯类化合物及甲基取代产物的螺旋结构与旋光性进行了定量分析,检测结果证明了理论分析的正确性;对旋光值变化规律给予了合理解释.     

非手性聚合物体系中超分子手性的存储及自修复

从非手性组装基元出发构建超分子手性材料一直是手性研究领域的一个挑战性课题,其不仅可以避免复杂的合成步骤与使用昂贵的手性原料,而且可以从本质上理解手性材料中手性的起源究竟是什么.一般的手性诱导均依赖于非共价键相互作用作为手性传递的媒介,但这一弱相互作用很容易受到外界环境例如温度、光照以及溶剂的影响从而导致手性组装结构被破坏.近日,苏州大学张伟等在非手性侧链型液晶聚合物体系中,结合手性诱导与共价键交联的方式实现了超分子手性的长久记忆,并且这一有序结构仍可对外界条件的改变做出响应.即使手性被短暂擦除,其也可依赖存储于共价交联网络中的手性信息实现手性自修复(chiral self-recovery).这一工作有望为未来多功能手性材料的设计提供新的思路.     

Chiral Induction and Remote Chiral Communication in Quinoline Oligoamide Foldamers for Determination of Enantiomeric Excess and Absolute Configuration of Chiral Amines and Their Derivatives

Two pentameric foldamers, Q5 and Q5C-S , containing a C−F bond were synthesized based on quinoline oligamide foldamers for the measurement of enantiomeric excess and for the determination of absolute configuration of chiral amines, diamines, amino alcohols, and α-amino acid esters. Chiral induction of Q5 was triggered in situ when the chiral analytes reacted with the C−F bond in Q5 by a N-nucleophilic substitution reaction, leading to a linear correlation between the CD amplitude at the region of quinoline chromophores and the ee values of the chiral analytes, which can be used for the ee determination of chiral analytes. Furthermore, the CD intensity of Q5C-S containing a chiral motif at its C-terminus enhances via remote, favorable chiral communication when the chiral induction was triggered in situ by chiral analytes at the N-terminus matches the original helicity of Q5C-S , but decreases via remote, conflicted chiral communication when the chiral induction is triggered in situ by chiral molecules at the N-terminus mismatches the original one. The system can thus be used for determination of the absolute configuration of chiral analytes, given that the chirality of the chiral motif at the C-terminus of Q5C-S is known.     

Chiral Phosphoric Acid-Catalyzed Enantioselective Synthesis of Axially Chiral Compounds Involving Indole Derivatives

Indoles are one of the most ubiquitous subclass of N-heterocycles and are increasingly incorporated to design new axially chiral scaffolds. The rich profile of reactivity and N−H functionality allow chemical derivatization for enhanced medicinal, material and catalytic properties. Although asymmetric C−C coupling of two arenes gives the most direct access of axially chiral biaryl scaffolds, this chemistry has been the remit of metal catalysis and works efficiently on limited substrates. Our group has devoted special interest in devising novel organocatalytic arylation reactions to fabricate biaryl atropisomers. In this realm, indoles and derivatives have been reliably used as the arylation partners in combination with azoarenes, nitrosonapthalenes and quinone derivatives. Their efficient interaction with chiral phosphoric acid catalyst as well as the tunability of electronics and sterics have enabled excellent control of stereo-, chemo- and regioselectivity to furnish diverse scaffolds. In addition, indoles could act as nucleophiles in desymmetrization of 1,2,4-triazole-3,5-diones. This account provides a succinct illustration of these developments.     

Co-Assembly of Chiral Amines and a Four-Armed Cyano-Substituted Luminophore through Hydrogen Bonds for Potential Development of Smart Chiroptical Materials

Chirality transfer from chiral molecules to assemblies is of vital importance to the design of functional chiral materials. In this work, selective co-assembly behaviors between chiral molecules and an achiral luminophore, potentially driven by the intermolecular salt-bridge type hydrogen bonds are reported. Cyano-substituted tetrakis(arylthio)benzene carboxylic acid ( TA ) served as the luminophore and hydrogen bond donors, which underwent co-assembly with different chiral amines. It was found that structures of chiral amines affect the chirality transfer and the properties of co-assemblies due to effects on hydrogen bonds and stacking pattern. Only in specific co-assemblies, the chiroptical properties occurred at both ground state and excited states based on the emerged Cotton effects and circularly polarized luminescence (CPL) signals, revealing that the chirality was successfully transferred from molecular level to supramolecular level. In addition, accurate quantitative examination of chiral amines was realized by circular dichroism (CD) spectra. This work demonstrates the characteristic chirality response and transfer through co-assembly, providing a potential method to develop smart chiroptical materials.     

Synthesis and Resolution of Planar–Chiral Ruthenium–Palladium Complexes with ECE′ Pincer Ligands

Feel the pinch! Planar–chiral, cationic, ruthenium–palladium complexes based on η⁶,η¹‐coordinated ECE′ pincer ligands are synthesized as racemic mixtures by reacting ECE′–palladium complexes and [Ru(C₅R₅)(MeCN)₃]⁺ arenophiles (R=H or Me). Chiral resolution of the cationic complexes was achieved by using the chiral counterion [Δ‐TRISPHAT]^?, and solving the X‐ray crystal structure of one diastereoisomer (shown here).

     

Synthesis and Chemistry of New Central and Planar Chiral Sulfur-Containing Ferrocenyl Compounds

Abstract

Enantiomerically pure 2-hydroxyalkyl, 2-aminoalkyl and 2-iminoalkyl ferrocenyl p-tolylsulfides are easily prepared in good yields and with complete diastereocontrol from (S)-(2-p-tolylthio)ferrocencarboxyaldehyde. 2-Iminoalkyl ferrocenyl derivatives can be used as ligands in asymmetric catalysis and as starting materials for asymmetric Staudinger reaction.     

几种手性原子转移自由基聚合引发剂的合成及其在螺旋选择性聚合中的应用

合成了(S)-2,2'-二(溴甲基)-1,1'-联萘, (S)-2'-甲基-2-溴甲基-1,1'-联萘, α-溴代苯乙酸薄荷酯, N-薄荷基-α-溴代苯乙酰胺和α-溴代苯乙酸胆甾烷醇酯5种旋光的溴代烷并将其用作非手性单体甲基丙烯酸-1-苯基二苯并环庚醇酯 (PDBSMA)的原子转移自由基聚合(ATRP)的手性引发剂. 为了使这些手性引发剂在引发一步生成的初级自由基不发生消旋化, 引发剂中的手性中心都不直接与溴原子相连. 用这5种手性溴代烷做引发剂引发PDBSMA的ATRP所得聚合物可分成四氢呋喃(THF)可溶部分和THF不溶部分. THF可溶部分具有较大的比旋光度. 对THF可溶部分的手性光学性质研究以及比较该部分聚合物和在同样引发条件下得到的甲基丙烯酸甲酯聚合物的比旋光度, 我们得出聚合物大的比旋光度是由聚合物单手性螺旋过量引起的结论, 即合成的手性引发剂对PDBSMA的ATRP均有一定的螺旋选择性, 其中(S)-2,2'-二(溴甲基)-1,1'-联萘、(S)-2'-甲基-2-溴甲基-1,1'-联萘螺旋选择性最好. 引发剂的螺旋诱导能力跟聚合反应的温度有很大关系, 聚合温度上限为70 ℃, 在0～70 ℃之间, 随着温度的升高引发剂的螺旋选择性逐渐增强.     

Ferrocene derivatives with planar chirality and their enantioseparation by liquid-phase techniques

In the last decade, planar chiral ferrocenes have attracted a growing interest in several fields, particularly in asymmetric catalysis, medicinal chemistry, chiroptical spectroscopy and electrochemistry. In this frame, the access to pure or enriched enantiomers of planar chiral ferrocenes has become essential, relying on the availability of efficient asymmetric synthesis procedures and enantioseparation methods. Despite this, in enantioseparation science, these metallocenes were not comprehensively explored, and very few systematic analytical studies were reported in this field so far. On the other hand, enantioselective high-performance liquid chromatography has been frequently used by organic and organometallic chemists in order to measure the enantiomeric purity of planar chiral ferrocenes prepared by asymmetric synthesis. On these bases, this review aims to provide the reader with a comprehensive overview on the enantioseparation of planar chiral ferrocenes by discussing liquid-phase enantioseparation methods developed over time, integrating this main topic with the most relevant aspects of ferrocene chemistry. Thus, the main structural features of ferrocenes and the methods to model this class of metallocenes will be briefly summarized. In addition, planar chiral ferrocenes of applicative interest as well as the limits of asymmetric synthesis for the preparation of some classes of planar chiral ferrocenes will also be discussed with the aim to orient analytical scientists towards ‘hot topics’ and issues which are still open for accessing enantiomers of ferrocenes featured by planar chirality.