Synthesis of Chiral Ionic Polymers Containing Quaternary Ammonium Sulfonate Structure and their Catalytic Activity in Asymmetric Alkylation

Repeated reaction between chiral quaternary ammonium dimer and disodium disulfonate gave the ionic polymer, which contains chiral quaternary ammonium sulfonate structure as a repeating unit. This chiral ionic polymer showed an excellent catalytic activity in asymmetric alkylation reaction. With the chiral ionic polymer catalysts, high level of enantioselectivities up to 97% ee were attained.     

Cover Picture: Journal of the Chinese Chemical Society 7/2012

Repeated reaction between chiral quaternary ammonium halide dimer and disodium disulfonate gave the ionic polymer, which contains chiral quaternary ammonium sulfonate structure as a repeating unit. This chiral ionic polymer showed an excellent catalytic activity in asymmetric benzylation reaction. With the chiral ionic polymer catalysts, high level of enantioselectivities up to 97% ee were attained. For more details on this figure, please see pp 815～821 in this issue.     

3-Alkoxymethyl-1-(1R,2S,5R)-(−)-menthoxymethylimidazolium salts-based chiral ionic liquids

A new group of imidazolium salt-based chiral ionic liquids have been prepared and characterized. The chiral ionic liquids obtained are stable in air, in contact with water and popular organic solvents. Their physicochemical properties, single-crystal X-ray structures, antimicrobial activities, and antielectrostatic effects have been determined. The chiral ionic liquids synthesized have proven to represent not only potential new solvents in asymmetric synthesis but also effective disinfectants with antielectrostatic activity.     

Symmetry Breaking in Chiral Ionic Liquids Evidenced by Vibrational Optical Activity

Ionic liquids (ILs) are receiving increasing interest for their use in synthetic laboratories and industry. Being composed of charged entities, they show a complex and widely unexplored dynamic behavior. Chiral ionic liquids (CILs) have a high potential as solvents for use in asymmetric synthesis. Chiroptical methods, owing to their sensitivity towards molecular conformation, offer unique possibilities to study the structure of these chiral ionic liquids. Raman optical activity proved particularly useful to study ionic liquids composed of amino acids and the achiral 1‐ethyl‐3‐methylimidazolium counterion. We could substantiate, supported by selected theoretical methods, that the achiral counterion adopts an overall chiral conformation in the presence of chiral amino acid ions. These findings suggest that in the design of chiral ionic liquids for asymmetric synthesis, the structure of the achiral counter ion also has to be carefully considered.     

Molecular design of chiral quaternary ammonium polymers for asymmetric catalysis applications

Repeated reaction between a chiral quaternary ammonium dimer and disodium disulfonate gave a chiral ionic polymer, which showed excellent catalytic activity in the asymmetric benzylation of N-diphenylmethylene glycine tert-butyl ester.     

功能化的离子液体: 手性离子液体的合成与应用

手性在化学中占有重要地位. 利用离子液体特殊的结构可调性质, 将手性引入到离子液体结构中, 可以获得具有手性的离子液体, 从而可能广泛应用于手性合成、手性分离、手性催化等领域. 汇总了至今报道的手性离子液体, 从离子液体功能化设计的角度探讨其合成方法. 针对手性离子液体可能的发展方向, 再次强调了由天然手性源设计合成离子液体遵循的三个标准.     

离子液体功能化手性salen Mn(Ⅲ)配合物不对称催化仲醇氧化动力学拆分反应

采用共价键联法,将亲水性咪唑类离子液体结构引入手性salen Mn(Ⅲ)配合物的C5位,制备了离子液体功能化手性salen Mn(Ⅲ)配合物.傅里叶变换红外光谱、紫外光谱和旋光分析等结果表明,咪唑类离子液体结构已嫁接到手性salen Mn(Ⅲ)配合物结构中,且嫁接过程未破坏催化活性中心.在以PhI(OAc)2为氧化剂,H2O/CH2Cl2为溶剂的(+/-)-α-甲基苯甲醇不对称氧化动力学拆分反应中,该催化剂表现出比传统手性salen Mn(Ⅲ)催化剂更高的催化活性,仲醇的转化率达到63%以上,对映选择性为99%,拆分效率为18.3%.可通过调变溶剂实现催化剂的分离并重复使用3次以上.实验结果表明,亲水性咪唑离子液体可改善水相反应传质问题且有利于稳定催化活性中间体,从而提高催化活性及稳定性.     

A chiral Mn(III) salen complex immobilized onto ionic liquid modified mesoporous silica for oxidative kinetic resolution of secondary alcohols

A supported ionic liquid strategy has been applied for the immobilization of a chiral Mn(III) salen complex onto ionic liquid modified mesoporous silica SBA-15. The immobilized catalyst demonstrated high enantioselectivity and activity in the oxidative kinetic resolution of secondary alcohols, and could be recycled five times without obvious loss of activity.     

Single-walled carbon nanotubes for improved enantioseparations on a chiral ionic liquid stationary phase in GC

In order to investigate whether the use of single-walled carbon nanotubes can improve enantioseparations on an ionic liquid stationary phase, a chiral ionic liquid, (R)-N,N,N-trimethyl-2-aminobutanol-bis(trifluoromethanesulfon)imidate, was synthesized. Two capillary columns, one containing the chiral ionic liquid and the other containing the single-walled carbon nanotubes and the chiral ionic liquid, were then prepared for GC. The results of the separations achieved with these columns show that coating the chiral ionic liquid stationary phase onto the capillary column containing single-walled carbon nanotubes improves the enantioselectivety of the chiral ionic liquid. This work indicates that using single-walled carbon nanotubes in this manner enables the application range of such GC chiral separations to be extended.     

Recent developments on chiral ionic liquids: design, synthesis, and applications

The recent progress in chiral ionic liquids with respect to their syntheses and applications in enantioselective reactions and chiral recognition is described. In addition to the conventional chiral ionic liquids derived from chiral natural products, a library of novel chiral spiro compounds, including spiro bis(pyridinium) and spiro bis(imidazolium) salt, is also described.     

Functionalized Chiral Ionic Liquids: A New Type of Asymmetric Organocatalysts and Nonclassical Chiral Ligands

By judiciously anchoring functional groups onto chiral ionic liquids, functionalized chiral ionic liquids (FCILs) are emerging as a new type of asymmetric organocatalysts and nonclassical chiral ligands. This Focus Review highlights the applications of FCILs from the viewpoint of asymmetric catalysis. We focus mainly on the de novo designed and synthesized FCILs which likely still maintain the typical ionic liquids properties, and in a few cases relevant ionic liquid immobilized chiral catalysts are briefly discussed.     

Natural terpene derivatives as new structural task‐specific ionic liquids to enhance the enantiorecognition of acidic enantiomers on teicoplanin‐based stationary phase by high‐performance liquid chromatography

We present the specific cooperative effect of a semisynthetic glycopeptide antibiotic teicoplanin and chiral ionic liquids containing the (1R ,2S ,5R )‐(–)‐menthol moiety on the chiral recognition of enantiomers of mandelic acid, vanilmandelic acid, and phenyllactic acid. Experiments were performed chromatographically on an Astec Chirobiotic T chiral stationary phase applying the mobile phase with the addition of the chiral ionic liquids. The stereoselective binding of enantiomers to teicoplanin in presence of new chiral ionic liquids were evaluated applying thermodynamic measurements and the docking simulations. Both the experimental and theoretical methods revealed that the chiral recognition of enantiomers in the presence of new chiral ionic liquids was enthalpy driven. The changes of the teicoplanin conformation occurring upon binding of the chiral ionic liquids are responsible for the differences in the standard changes in Gibbs energy (ΔG ⁰) values obtained for complexes formed by the R and S enantiomers and teicoplanin. Docking simulations revealed the steric adjustment between the chiral ionic liquids cyclohexane ring (chair conformation) and the β‐d ‐glucosamine ring of teicoplanin and additionally hydrophobic interactions between the decanoic aliphatic chain of teicoplanin and the alkyl group of the tested salts. The obtained terpene derivatives can be considered as “structural task‐specific ionic liquids” responsible for enhancing the chiral resolution in synergistic systems with two chiral selectors.     

Synthesis and characterization of novel chiral imidazolium and pyridinium ionic liquids derived from tartaric acid and 2-oxazolidinone

Abstract

Novel chiral imidazolium and pyridinium ionic liquids based on tartaric acid and 2-oxazolidinone were designed. Symmetrical dicationic ionic liquids based on tartaric acid have been synthesized and characterized. These chiral ionic liquids were designed by employing very short and simple methods. Incorporation of alkyl halide over tartaric acid and 2-oxazolidinone is an important step. N-methyl imidazole and pyridine were used for preparation of quaternary salts. These ionic liquids have been evaluated for the asymmetric sulfide oxidation. Chiral ionic liquids based on tartaric acid showed superior chiral inducing property as compare to 2-oxazolidinone based chiral ionic liquids.     

Chiral metal-containing ionic liquid:Synthesis and applications in the enantioselective cycloaddition of carbon dioxide to epoxides

A series of novel chiral metal-containing ionic liquids(CMILs) consisting of the cation of crown ether-chelated potassium/sodium and the anion of chiral amino acids were designed and synthesized.These new CMILs were used to catalyze the enantioselective cycloaddition of epoxides and carbon dioxide incorporating with the salenCo(OOCCCl3) to generate corresponding chiral cyclic carbonates under mild conditions.These new catalysts can be recycled at least five times without significant loss of activity and ena...     

(S)-Histidine: the ideal precursor for a novel family of chiral aminoacid and peptidic ionic liquids

(S)-Histidine is shown to be a powerful chiral precursor for the construction of a new series of imidazolium-containing chiral ionic liquids, in which the chiral bifunctional unit of the aminoacid remains unchanged. These ionic materials can be used as building blocks for the synthesis of peptidic ionic liquids.     

Combinatorial synthesis of functionalized chiral and doubly chiral ionic liquids and their applications as asymmetric covalent/non-covalent bifunctional organocatalysts

A facile combinatorial strategy was developed for the construction of libraries of functionalized chiral ionic liquids (FCILs) including doubly chiral ionic liquids and bis-functional chiral ionic liquids. These FCIL libraries have the potential to be used as asymmetric catalysts or chiral ligands. As an example, novel asymmetric bifunctional catalysts were developed by simultaneously incorporating functional groups onto the cation and anion. The resultant bis-functionalized CILs showed significantly improved stereoselectivity over the mono-functionalized parent CILs.     

Synthesis of novel chiral imidazolium-based ionic liquids derived from isosorbide and their applications in asymmetric aza Diels-Alder reaction

A novel family of chiral imidazolium-based ionic liquids containing a chiral moiety and a free hydroxyl function has been designed and synthesized using isosorbide as a biorenewable substrate. These chiral ionic liquids were found to catalyze the aza Diels-Alder reaction to give good yields and moderate diastereoselectivities. Chiral ionic liquids are recycled while their efficiency is preserved.     

Use of chiral ionic liquids as solvents for the enantioselective photoisomerization of dibenzobicyclo[2.2.2]octatrienes

[Reaction: see text] Six chiral ionic liquids were prepared and evaluated as "chiral induction solvents" in which two different dibenzobicyclo[2.2.2]octatrienes were photoisomerized to chiral products. Enantiomeric excesses from 3 to 12% were obtained from the photochemical di-pi-methane rearrangement. Results indicate that the chiral induction derives from an ion pairing interaction of the deprotonated diacids with the ionic liquid cation. This is the first report on chiral induction via a chiral IL for an irreversible, unimolecular photochemical isomerization.     

(R)‐N,N,N‐Trimethyl‐2‐Aminobutanol‐Bis(Trifluoromethane‐Sulfon)Imidate Chiral Ionic Liquid Used as Chiral Selector in HPCE,HPLC, and CGC

Abstract

In this work, the (R)‐N,N,N‐trimethyl‐2‐aminobutanol‐bis(trifluoromethanesulfon)imidate chiral ionic liquid was first used in chromatography and exhibited a excellent chiral recognition ability in high performance capillary electrophoresis (HPCE), high performance liquid chromatography (HPLC), and capillary gas chromatography (CGC), which also showed for the first time that chrial ionic liquid was an effective chiral selector in HPCE and HPLC. The compounds that have been separated using this chiral ionic liquid at least included alcohol, amine, acid, and amino acid, et al. enantiomers. As the chiral ionic liquid can be easily synthesized from relatively inexpensive materials, it should have a great potentiality for chiral separation in chromatographic science.     

Synthesis of chiral ionic liquids from natural amino acids

For the first time, chiral imidazolium ionic liquids containing one chiral carbon (10a-c) were synthesized from the natural amino acids by a simple and straightforward procedure. The characteristics of the chiral ILs are very similar to the popular ionic liquids.