Acetic acid functionalized ionic liquid systems: An efficient and recyclable catalyst for the regioselective ring opening of epoxides with NaN3

In the present study, an environmentally benign, efficient, and solvent-free procedure was developed for the synthesis of 1,2-azidoalcohols by the regioselective ring opening of some epoxides with sodium azide (NaN₃) in the presence of an acetic acid functionalized imidazolium salt [Cmmim]BF₄ or [Cmmim]Br as a green and Brønsted acidic ionic liquid (BAIL) catalyst under mild and neutral reaction conditions at 60 °C. The remarkable features of this procedure are excellent regioselectivity, simple work-up procedure, high yields of products, short reaction times, and ease of recyclability of ionic liquids.     

Task-oriented use of ionic liquids: efficient acetylation of alcohols and phenols

The ionic liquid 1-butyl-3-methylimidazolium acetate proves to be an excellent reaction medium for the acetylation of alcohols and phenols, providing better conditions than the acidic 1-butyl-3-methylimidazolium bisulfate. Reactions were carried at room temperature, with only a 10% excess of acylating agent and with no other solvent or catalyst added.     

Polystyrene-supported chloroaluminate ionic liquid as a new heterogeneous Lewis acid catalyst for Knoevenagel condensation

Non-hygroscopic polystyrene-supported chloroaluminate ionic liquid was prepared from the reaction of Memfield resin with 1- methylimidazole followed by reaction with aluminum chloride.This Lewis acidic ionic liquid is environmentally friendly heterogeneous catalyst for the Knoevenagel condensation of aromatic and aliphatic aldehydes with ethyl cyanoacetate.The catalyst is stable(as a bench top catalyst) and reusable.     

An efficient preparation and characterization of 1-(2-ethoxy-2-oxoethyl)imidazolium based ionic liquids derivatives as potential bioactive agents

A set of new 1-(2-ethoxy-2-oxoethyl)imidazolium-based ionic liquids (1–16) have been prepared via the alkylation reaction of ethyl 2-(1H-imidazol-1-yl)acetate with various type of substituted alkyl halides using a microwave irradiation reaction in yields above 90%. The chemical structures of the manufactured ILs (1–16) were analyzed by mass and NMR spectroscopy. The newly prepared ILs were examined for their in vitro anti-microbial activities towards different types of Gram (+) and Gram (−) bacteria, and also for their antifungal activities. The preliminary tests showed that most of the resultant ILs presented modest activities towards S. aureus and B. subtilis with IZ values ranging between 10 and 14 mm, while the E. coli activities was in the range of 16 and 20 mm. However, ILs (1–16) displayed poor activities against the C. albicans.     

A new liquid crystal compound based on an ionic imidazolium salt

The preparation of 1,3-bis-(4-dodecyloxy-phenyl)-3H-imidazol-1-ium trifluoro-methanesulfonate is described from the 4-dodecyloxy phenylamine derivative. This new imidazolium salt exhibits a lamellar liquid crystal mesophase between 119 and 172 °C. The Smectic A phase has been characterised by polarising optical microscopy, differential scanning calorimetry and X-ray diffraction. In addition the lamellar crystallographic structure obtained on single crystal is reported and corroborated the self-assembly of molecules in the mesomorphic state.     

An ionic liquid-tagged second generation Hoveyda-Grubbs ruthenium carbene complex as highly reactive and recyclable catalyst for ring-closing metathesis of di-, tri- and tetrasubstituted dienes

A second generation Hoveyda-Grubbs ruthenium carbene complex bearing an ionic liquid tag was prepared and shown to be a highly reactive catalyst for the ring-closing metathesis of di-, tri- and tetrasubstituted diene and enyne substrates in minimally ionic solvent systems ([Bmim]PF₆/CH₂Cl₂, 1:9-1:1 v/v). Both the catalyst and the ionic liquid can be conveniently recycled and repeatedly reused (up to 17 cycles) with only a very slight loss of activity. The ionic liquid tag is crucial to the high level of recyclability of the catalyst since the original second generation Grubbs and Hoveyda-Grubbs catalysts rapidly lose their activity when recycled in the ionic liquid layer.     

An imidazolium ionic liquid having covalently attached an oxime carbapalladacycle complex as ionophilic heterogeneous catalysts for the Heck and Suzuki-Miyaura cross-coupling

An oxime carbapalladacycle, analogous to that used as catalyst in homogeneous phase, has been derivatized to increase its ionophilicity by introducing an imidazolium group covalently attached through a chain at the complex. The resulting complex is soluble in 1-butyl-3-methylimidazolium ionic liquid (bmimPF₆) and not extractable by ether. The catalytic activity of this palladium complex in bmimPF₆ is, however, unsatisfactory and only increases marginally in bmimPF₆/supercritical CO₂. This limitation has been overcome by supporting this imidazolium palladium complex on high surface area Al/MCM-41 aluminosilicate, whereby a solid active catalyst for the Suzuki cross-coupling has been obtained. Reusability and stability over reuse for this Al/MCM-41-supported catalyst have been studied.     

Metal-containing ionic liquids and ionic liquid crystals based on imidazolium moiety

Ionic liquids and ionic liquid crystals of imidazolium salts composed of various transition and main group metals have been reviewed. Ionic metal complexes of imidazoles and N-heterocyclic carbenes possess the similar properties were also included. These types of ILs and ILCs have been realized as potential solvents, catalysts, catalyst precursors and reagents for many organic transformations and provide ecofriendly protocols. They have also been found to play key roles in material science. Many of these IL systems are air- and moisture stable and are considered as alternatives for air- and moisture sensitive chloroaluminate-based ILs.     

Thiazolinium salt: an efficient catalyst for the Mukaiyama reaction

Mukaiyama aldol reaction between benzaldehyde and Danishefsky diene is promoted by ionic liquid-type salts. Hence, thiazolinium salts have been found to be the most efficient for this transformation. On a mechanistic point of view, only the Mukaiyama process is observed without any hetero Diels-Alder cycloaddition. In some cases, cyclisation of the Mukaiyama adduct occurred without addition of TFA. Interestingly, the thiazolinium catalyst can be recycled at least 10 times without loss of activity.     

Transition-metal free ring deuteration of imidazolium ionic liquid cations

A simple, low-cost and transition-metal free ring deuteration procedure applicable to ionic liquids (ILs) with imidazolium cations has been developed. Reaction profiles for the exchange have been measured.     

An efficient one-pot synthesis of 3-glyoxylic acids of electron-deficient substituted azaindoles by ionic liquid imidazolium chloroaluminate-promoted Friedel-Crafts acylation

An efficient, one-pot Friedel-Crafts acylation/hydrolysis reaction promoted by the acidic ionic liquid 1-ethyl-3-methylimidazolium chloroaluminate (generated from 1-ethyl-3-methylimidazolium chloride (EmimCl) and aluminum chloride (X(AlCl₃), mole fraction X = 0.75) for the formation of 3-glyoxylic acid derivatives of electron-deficient, substituted 4- and 6-azaindoles is described.     

Selenonium ionic liquid as efficient catalyst for the Baylis-Hillman reaction

The new acidic ionic liquid phenyl butyl ethyl selenonium tetrafluoroborate, [pbeSe]BF₄, was successful used as a co-catalyst in the Baylis-Hillman reaction of aldehydes and electron-deficient alkenes. The Baylis-Hillman adducts were obtained in moderated to good yields and in relatively short reaction times under mild conditions.     

室温下以原位生成的醋酸咪唑鎓盐为催化剂和酰化剂用于醇、酚和胺的乙酰化反应(英文)

Acylimidazolium acetate was readily prepared in situ from the reaction of imidazole with acetic anhydride and subsequently acted as a catalyst and acylating agent for the efficient acetylation of alcohols, phenols, and amines at ambient temperature.     

A highly active ionic liquid catalyst for Morita-Baylis-Hillman reaction

The Morita-Baylis-Hillman reaction is an efficient carbon-carbon bond forming reaction for the preparation of α-methylene-β-hydroxycarbonyl compounds. A new and highly active di-naphthalene imidazolium salt has been synthesized. We have found that 1,3-bis[2-(naphthalene-2-yloxy)propyl]imidazolium bromid promoted the Morita-Baylis-Hillman reaction of various aryl aldehyde compounds in the absence of solvents. Our studies show that the Morita-Baylis-Hillman reaction by the influence of ionic liquid to give a high yield and short reaction time.     

高效可循环离子型钯配合物催化羰化Sonogashira反应

炔酮类化合物作为一类具有生物活性的分子,是天然产物全合成中构建杂环类化合物的重要中间体.炔酮类化合物的传统合成方法是通过过渡金属催化金属有机炔烃和酰氯的交叉偶联,但存在酰氯本身稳定性和底物官能团耐受力较差的缺点.近年来,钯催化的羰化Sonogashira反应(末端炔烃和芳基卤化物与CO的偶联反应)成为合成炔酮类化合物更为直接和有效的方法,其中与钯中心原子配位的配体的电子效应和空间效应可显著调控钯配合物的催化性能.但均相钯催化的羰化Sonogashira反应体系存在催化剂流失、分离困难和难以循环使用的问题.我们以2-(1-咪唑基)噻唑为母体分子,合成了具有P,S,N杂合配体特征的配体L1,同时将配体L1通过与MeOTf的季铵化反应得到相应的离子型膦配体L2.在此基础上,利用L1和L2与过渡金属中心的配位作用合成相应的钯配合物1A和2A.由于L1和L2中含有多种不同配位能力的配体(P-配体,S-配体和/或N-配体),故通过N/S杂原子对Pd-中心原子的协同弱配位作用,可以调变相应钯配合物对羰化Sonogashira反应的催化性能.另外,2A中具有强吸电子效应的正电荷的存在,使其结构和催化性能也必然不同于中性配合物1A.实验结果表明,在温和的反应条件(90℃,lh,CO压强1.0 MPa)下,对于碘苯和苯乙炔的羰化Sonogashira偶联反应,1A体现出优于2A的催化性能,TOF值达到840 h-1;但反应温度提高到120℃时,1A的TOF高达3560 h-1,2A的TOF为2960 h-1.与L1的2JP-Se=744 Hz相比,L2的2JP-Se=768 Hz,说明L2中具有吸电子效应的正电荷的存在降低了相应P原子的σ给电子能力(2JP-Se数值越大,相应膦配体的6给电子能力越弱);同时,1A中具有弱配位能力的N配体的缺失削弱了配体对Pd活性中心的稳定作用.在底物普适性研究中发现,4-硝基溴苯在相同反应条件下几乎得不到羰化Sonogashira偶联产物.而将反应体系中的CO换为同样压强下的N2,却可以顺利实现Sonogashira偶联反应.我们推测,在CO氛围下形成的pd0-CO活性物种(与N2氛围下形成的Pd0活性物种相比)具有相对较低的对底物的氧化加成能力.离子型钯配合物2A的优势在于,当将其与室温离子液体[Bmim]PF6(溶剂)结合使用,在2A催化碘苯与苯乙炔的羰化Sonogashira偶联反应过程中,循环使用8次催化性能没有明显下降.     

Increased paraoxon detection by acetylcholinesterase inactivation with ionic liquid additives

This is the first study using ionic liquids (ILs) as additive in the aqueous solvent medium for detection of paraoxon by acetylcholinesterase inhibition method. A systematic comparison of various ILs with organic solvents has been made. The aqueous buffer solution containing ionic liquid ethylpyridinium hexafluorophosphate [EtPy]⁺[PF₆]⁻ has been found to give the best results. The inhibition kinetic follows the first order model. Ionic liquids modified aqueous solutions show the potential to provide a promising and effective medium in detection of paraoxon with acetylcholinesterase.     

Bimetallic PdAu nanoparticles as hydrogenation catalysts in imidazolium ionic liquids

Metallic and bimetallic PdAu nanoparticles were solubilized in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid (IL) by a phase-transfer method using poly(vinylpyrrolidone) (PVP) as a stabilizer. Nanoparticles were characterized by UV–vis spectroscopy and transmission electron microscopy. The bimetallic PdAu nanoparticles in the IL-phase were examined as catalysts for hydrogenation reactions; both the activity and selectivity of the hydrogenation reactions could be tuned by varying the composition of the bimetallic nanoparticles, with maximum activities seen at 1:3 Au:Pd ratios. These nanoparticles/IL catalysts were recycled and then reused for further catalytic reactions with minimal loss in activity.     

An efficient protocol for the preparation of pyridinium and imidazolium salts based on the Mitsunobu reaction

We report herein that, in the absence of any nucleophilic counterions, tertiary nitrogen nucleophiles such as pyridines and imidazoles can be alkylated with alcohols, by simply using their ammonium form as the acidic component of the Mitsunobu reaction. This led to efficient preparation of ionic liquids under mild conditions, avoiding the usual anion exchange step.     

A facile and economical procedure for the synthesis of maleimide derivatives using an acidic ionic liquid as a catalyst

Seven maleimide derivatives were synthesized in good yields and high purity from the corresponding maleamic acids using a Brønsted acidic room temperature ionic liquid (RTIL) as a catalyst. The products were obtained through merely a decanting and removal of the solvent, suggesting that this procedure is superior to the conventional routes, in which the strong organic/inorganic acids were used as the catalysts, as well as a complicated post-processing procedure for the separation and purification of the products was employed.     

Synthesis of Fischer indole derivatives using carboxyl-functionalized ionic liquid as an efficient and recyclable catalyst

Fischer indole cyclization of phenylhydrazine and various ketones using carboxyl-functionalized ionic liquid, 1-carboxymethyl-3-methylimidazolium tetrafluoroborate (abbreviated as [cmmim][BF4]) as catalyst was successfully performed. The yields of thetarget compounds were 80-92%, the purities were 96-98%. The catalyst could be rocovered and reused for at least six times without significant loss in activity.