Efficient Suzuki-Miyaura coupling of (hetero)aryl chlorides with thiophene- and furanboronic acids in aqueous n-butanol

An efficient Suzuki cross-coupling protocol enables the reaction of N-hetero and normal aryl chlorides with thiophene- and furanboronic acids. Coupling is effected in aqueous n-butanol as the solvent in near quantitative yield with a catalyst loading of 0.1-1 mol %. For heterocyclic substrates aqueous catalysis is found to be more efficient than Suzuki coupling under anhydrous conditions. The developed Suzuki coupling procedure utilizes biodegradable solvents and is useful for large scale reactions, as it includes the facile product separation from a biphasic solvent mixture without the need for additional organic solvents during workup.     

液/液两相催化新进展--温控非水液/液两相催化

温控非水液/液两相催化,是指一类由两种或多种液态有机物组成的催化反应体系,其特点是体系的相态变化可通过温度来调控,即体系在高温时相互混溶呈均相,低温不溶分成两相,催化剂和产物分别处于两相,从而为解决均相催化剂分离难的问题开拓了一个新方向,是液/液两相催化研究领域最引人注目的进展之一.首次以"温控"为主线将氟两相催化作为温控液/液两相催化的一个特定类型纳入"温控非水液/液两相催化"范畴,并与其它通过温度来调控的有机液/液两相和作者提出的温控相分离催化串在一起作一较为详细的评述.     

温控配体与液／液两相催化

 以作者近年的研究工作为主，对液／液两相催化研究领域取得的进展做一综述．着重介绍了以温控配体为基础的新型液／液两相催化过程温控相转移催化（thermoregulatedphasetransfercatalysis，TRPTC）和温控相分离催化（thermoregulatedphase－separablecatalysis，TPSC）的基本原理及其在高碳烯烃氢甲酰化、芳香硝基化合物的CO选择性还原及烯烃加氢等反应中的应用．基于温控配体在水中的“浊点”特性而提出的温控相转移催化概念，为从根本上解决水／有机两相催化 的适用范围受底物水溶性限制的问题提供了一条新途径．而利用温控配体在某些有机溶剂中存在临界溶解温度（CST）的特性而实现的温控相分离催化，则使在高于临界溶解温度的反应温度时为均相的反应体系，在低温（＜CST）时则分成两相，催化剂自成一相，形成一种具有“均相反应、两相分离”特色的液／液两相催化新体系．     

离子液体两相不对称氢甲酰化催化反应的研究

从(R)-BINAP出发制备水溶性磺酸钠盐配体(R)-BINAPS,采用离子液体BF4和PF6为介质,实现其Rh配合物对乙酸乙烯酯的两相不对称氢甲酰化反应.实验结果表明,在以BF4为介质的乙酸乙烯酯不对称氢甲酰化反应中,该催化剂在温和条件下显示出高于相应均相体系的产物ee值和异构醛选择性,并在6次循环使用中,反应产物的ee值、选择性和转化率均无明显改变;在离子液体体系中添加适当的甲苯时,油溶性配体(R)-BINAP与Rh组成的配合物催化剂亦可形成类似的两相反应体系,但其活性和选择性在重复使用中呈明显下降趋势.本文还考察了溶剂体系、膦铑比、温度、压力、时间等的影响,并尝试苯乙烯的两相不对称氢甲酰化反应.     

Liquid-liquid biphasic synthesis of long chain wax esters using the Lewis acidic ionic liquid choline chloride·2ZnCl2

The first liquid-liquid biphasic synthesis of wax esters in a Lewis acidic ionic liquid, choline chloride·2ZnCl₂ by the esterification of long chain carboxylic acids with long chain alcohols is described. The reported reaction system has the advantages of both homogeneous and heterogeneous catalysis with high product yield and the ease of product as well as catalyst separation without the use of an organic solvent. The ionic liquid studied plays the dual role of solvent as well as catalyst and is recycled up to six times without any significant loss of activity.     

Ionic liquids as a medium for enantioselective catalysis

Over the last years, interest involving ionic liquids (ILs) used as reaction medium for homogeneous enantioselective catalysis has exponentially expanded. In many cases, the use of ILs provides several advantages over reactions in organic solvents in terms of activity and enantioselectivity. Even more important, the catalyst immobilization in IL can avoid its leaching and consequently favour its recycling. This review deals with recent advances in the investigation of these new solvents in asymmetric catalysis. We go over enzymes, chiral organocatalysts and metal complexes containing chiral ligands used in enantioselective processes using ionic liquids, with special emphasis on the catalyst reuse and also the separation of organic products.     

A novel amphiphilic chiral ligand derived from D-glucosamine. Application to palladium-catalyzed asymmetric allylic substitution reaction in an aqueous or an organic medium, allowing for catalyst recycling

A novel amphiphilic phosphinite-oxazoline chiral compound, 2-methyl-4,5-[4,6-O-benzylidene-3-O-bis[4-((diethylamino)methyl)phenyl]phosphino-1,2-dideoxy-alpha-D-glucopyranosyl]-[2,1-d]-2-oxazoline (1), has been prepared from natural D-glucosamine hydrochloride. The newly prepared complex, [Pd(2-methyl-4,5-[4,6-O-benzylidene-3-O-bis[(4-((diethylmethylammonium)methyl)phenyl)]phosphino-1,2-dideoxy-alpha-D-glucopyranosyl]-[2,1-d]-2-oxazoline)(eta3-C3H5)]3+ x 3BF4- (3), is soluble in water and an efficient catalyst for asymmetric allylic substitution reaction in water or an aqueous/organic biphasic medium (up to 85% ee). This catalytic system offers an easy separation of the aqueous catalyst phase from the product phase and allows recycling of the catalyst phase. In addition, compound 1 also works as an effective ligand for the palladium-catalyzed reaction under conventional homogeneous conditions in an organic medium, in which the catalyst (Pd-1 complex) can be recovered by simple acid/base extraction and reused in the second reaction.     

Dy(OTf)3 Catalyzed Reaction of Indole with Aldehydes and Ketones in Ionic Liquids

The use of environmentally benign reaction media is very important in view of today' s environmentally con scious attitude. In connect with this, room temperature ionic liquids that are air and moisture stable have received a good deal of attention in recent years as novel solvent systems for organic synthesis. A number of reactions such as Friedel-Crafts reactions, Diels-Alder cycloadditions, hydrogenations, and Heck reactions have employed ionic liquids as solvents. Among them, the Friedel-Crafts reaction[1] is of great synthetic significance in view of laboratory synthesis and industrial production. Recent studies showed that Friedel-Crafts reaction of indole with carbonyl compounds proceeded readily in aqueous media. [2] However, the aqueous reactions suffer from some common problems,such as tedious work-up, reuse of catalyst and so on.     

CO(2)-expanded solvents: unique and versatile media for performing homogeneous catalytic oxidations

The work summarized here demonstrates a new concept for exploiting dense phase CO(2), media considered to be "green" solvents, for homogeneous catalytic oxidation reactions. According to this concept, the conventional organic solvent medium used in catalytic chemical reactions is replaced substantially (up to 80 vol %) by CO(2), at moderate pressures (tens of bars), to create a continuum of CO(2)-expanded solvent media. A particular benefit is found for oxidation catalysis; the presence of CO(2) in the mixed medium increases the O(2) solubility by ca. 100 times compared to that in the neat organic solvent while the retained organic solvent serves an essential role by solubilizing the transition metal catalyst. We show that CO(2)-expanded solvents provide optimal properties for maximizing oxidation rates that are typically 1-2 orders of magnitude greater than those obtained with either the neat organic solvent or supercritical CO(2) as the reaction medium. These advantages are demonstrated with examples of homogeneous oxidations of a substituted phenol and of cyclohexene by molecular O(2) using transition metal catalysts, cobalt Schiff-base and iron porphyrin complexes, respectively, in CO(2)-expanded CH(3)CN.     

Ionic Liquids-New "Solutions" for Transition Metal Catalysis

Ionic liquids are salts that are liquid at low temperature (<100 degrees C) which represent a new class of solvents with nonmolecular, ionic character. Even though the first representative has been known since 1914, ionic liquids have only been investigated as solvents for transition metal catalysis in the past ten years. Publications to date show that replacing an organic solvent by an ionic liquid can lead to remarkable improvements in well-known processes. Ionic liquids form biphasic systems with many organic product mixtures. This gives rise to the possibility of a multiphase reaction procedure with easy isolation and recovery of homogeneous catalysts. In addition, ionic liquids have practically no vapor pressure which facilitates product separation by distillation. There are also indications that switching from a normal organic solvent to an ionic liquid can lead to novel and unusual chemical reactivity. This opens up a wide field for future investigations into this new class of solvents in catalytic applications.     

温控Noyori配体的合成及在苯乙酮不对称氢转移反应中的应用

设计并合成了一种新型的聚乙二醇单甲醚(MPEG)修饰的温控Noyori配体.将其与[RuCl2.(p-cymene)]2络合形成的催化剂用于水/环己烷两相体系中苯乙酮不对称氢转移反应.以甲酸钠为氢源,考察了反应温度、时间、甲酸钠用量、底物与催化剂摩尔比以及溶剂用量等因素对催化反应的影响.结果表明,反应体系中含催化剂的水相具有浊点,并且催化剂显示出良好的不对称催化性能,在甲酸钠/苯乙酮/催化剂的摩尔比为300:100:1、环己烷/水体积比1:1及30℃的反应条件下反应6h,苯乙酮的转化率为99.7%,产物α-苯乙醇的对映选择性(e.e.)为93.9%.催化剂相易与产物相分离并与直接循环使用,循环使用的催化剂活性明显下降,但产物对映选择性仍保持不变.     

Thermoregulated Liquid/Liquid Biphasic Catalysis and Its Application

A brief overview of our recent research results of thermoregulated liquid/liquid biphasic catalysis is presented. Emphasis is given to the general principles of thermoregulated phase-transfer catalysis (TRPTC) and thermoregulated phase-separable catalysis (TPSC). In addition, the applications of TRPTC and TPSC in biphasic catalysis are also discussed. The introduction of TRPTC to biphasic system is free from the shortcomings of classical aqueous/organic two-phase catalysis, in which the application scope is restrained by the water solubility of the substrate. Meanwhile, TPSC provides a very simple and reliable way to deal with the separation of catalyst in homogeneous catalysis. The common advantages of TRPTC and TPSC are characterized by homogeneous catalysis coupled with convenient biphasic separation.     

A highly fluorous room-temperature ionic liquid exhibiting fluorous biphasic behavior and its use in catalyst recycling

[formula: see text] A novel fluorous room-temperature ionic liquid, 1-butyl-3-methyl-imidazolium tetrakis[p-[dimethyl(1H, 1H, 2H, 2H-perfluorooctyl)silyl]phenyl]-borate (1), was used as a solvent for the homogeneous hydrosilylation of 1-octene catalyzed by a fluorous version of Wilkinson's catalyst. The catalyst was recycled by biphasic separation with an average retention of catalyst activity of 94%. As opposed to other ionic liquids, 1 exhibits high miscibility with apolar compounds such as alkenes and resembles fluorous solvents in its phase behavior with organic solvents.     

SBA-15-functionalized palladium complex partially confined with ionic liquid: an efficient and reusable catalyst system for aqueous-phase Suzuki reaction

A novel SBA-15 functionalized palladium complex partially confined with 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid (Material 4) was found to be a very efficient and reusable catalyst in the Suzuki-Miyaura coupling reaction of aryl halides including aryl chlorides and heteroaryl halides with different aryl boronic acids under aqueous conditions without any organic co-solvents. Our studies showed that 4 is a more efficient catalyst in comparison with the catalyst not containing IL or catalyst with a higher ratio of IL. The materials were characterized by N(2)-sorption analysis, TGA and transmission electron microscopy before and after catalysis. While our studies showed that the catalyst can be successfully recycled and reused in at least 4 reaction runs, in contrast, several poisoning experiments and kinetic studies provide the notion that homogeneous (dissolved) species are responsible for the observed catalysis.     

Ionic liquid assisted synthesis of S-heterocycles

Some organic solvents are highly toxic, flammable, and even explosive. In particular, high vapor pressures and toxicity of certain volatile organic solvents may cause significant environmental problems. Therefore, alternative solvents or media with tunable and versatile solvation properties for conducting chemical reactions and materials synthesis have been actively sought. Ionic liquids have numerous applications not only as environmentally benign reaction media, but also as catalysts and reagents. Due to the increase of environmental consciousness in chemical research and industry, the challenge for a sustainable environment calls for clean procedures that avoid the use of harmful organic solvents. Due to the special properties of ILs (ionic liquids) such as wide liquid range, good solvating ability, negligible vapor pressure, non-inflammability, non-volatility, environment friendly medium, high thermal stability, good stability in air and moisture, easy recycling and rate promoters etc. they are used in organic synthesis. Therefore, ionic liquids have attracted the attention of chemists and act as catalyst and reaction medium in organic reactions with high activity. Highly efficient methods are explored for the preparation of S-heterocycles with the application of ILs as catalyst and reaction medium.     

Enantioselective hydrogenation of imines in ionic liquid/carbon dioxide media

The enantioselective hydrogenation of N-(1-phenylethylidene)aniline using cationic iridium complexes with chiral phosphinooxazoline ligands was studied as a chemical probe to assess the potential of ionic liquid/carbon dioxide (IL/CO2) media for, multiphase catalysis. The biphasic system leads to activation, tuning, and immobilization of the catalyst that would be impossible in classical organic solvent systems or in either of the two unconventional media separately. In particular it is demonstrated that (i) the presence of CO2 can be beneficial or even mandatory for efficient hydrogenation in the IL; (ii) the precursor is activated in the IL by anion exchange allowing one to use in situ catalysts; (iii) the anion of the IL greatly influences the selectivity of the catalyst; (iv) the products are readily isolated from the catalyst solution by CO2 extraction without cross contamination of IL or catalyst; and (v) the IL leads to enhanced stability of the catalyst. These results are corroborated and rationalized on the basis of the physicochemical properties of the biphasic medium and the chemical characteristics of the catalytic systems.     

Hydroformylation of 2,5‐norbornadiene in organic/aqueous two‐phase system and acceleration by cationic surfactants

The organic/aqueous biphasic hydroformylation of 2,5‐norbornadiene (NBD) was investigated for the first time using HRh(CO)(TPPTS)₃ (TPPTS: trisodium salt of tri(m‐sulphonylphenyl)phosphine) as the catalyst precursor. A comparison was made of homogeneous and biphasic systems. The optimum reaction parameters are discussed and the reaction mechanism is presented. In order to ensure the process attained high activity under moderate conditions, the effect of various cationic surfactants was tested in the biphasic hydroformylation of NBD. The results indicated that the hydroformylation of NBD in the biphasic system exhibited high activity and high selectivity to dialdehyde products under mild conditions. The addition of cationic surfactants markedly accelerated the reaction. A single long‐chain surfactant seemed to exert a greater impact on the hydroformylation of NBD than a double long‐chain surfactant. Moreover, the recycling of aqueous solution containing catalyst with or without surfactant was investigated. In the absence of the surfactant, the aqueous catalyst could be recycled six times without a significant decrease in activity and selectivity. Copyright © 2016 John Wiley & Sons, Ltd.     

离子液体载催化剂和载试剂在有机合成中的应用

综述了离子液体载催化剂和载试剂在有机合成中的应用进展. 离子液体载催化剂是针对离子液体中催化剂难以回收利用的问题提出来的, 它不仅可以实现均相催化, 而且反应产物容易分离, 催化剂可以循环使用. 离子液体载有机试剂合成, 又称为离子液体相有机合成, 具有固相反应产物纯度高和液相反应反应快的优点. 在离子液体载无机试剂的反应中, 反应物毒性降低, 反应条件温和, 产物选择性好.     

Overcoming Phase‐Transfer Limitations in the Conversion of Lipophilic Oleo Compounds in Aqueous Media—A Thermomorphic Approach

A new process concept has been developed for recycling transition‐metal catalysts in the synthesis of moderately polar products via aqueous thermomorphic multicomponent solvent systems. This work focuses on the use of “green” solvents (1‐butanol and water) in the hydroformylation of the bio‐based substrate methyl 10‐undecenoate. Following the successful development of a biphasic reaction system on the laboratory scale, the reaction was transferred to a continuously operated miniplant to demonstrate the robustness of this innovative recycling concept for homogenous catalysts.     

Catalysis in glycerol: a survey of recent advances

There is currently a significant increase in the use of glycerol as a renewable solvent for catalytic reactions. Glycerol has often been the solvent of choice in both homogeneous and heterogeneous catalyses, despite its high viscosity at ambient temperature and the low solubility of highly hydrophobic reagents found in glycerol. Its biodegradability and non-toxicity have led to reports of improved reaction performance and selectivity, as well as easier product separation and effective catalyst recycling. All relevant advances in this emerging field of “green” catalysis are thoroughly reviewed below.