A Dicationic Ruthenium Alkylidene Complex for Continuous Biphasic Metathesis Using Monolith‐Supported Ionic Liquids

A dicationic ruthenium–alkylidene complex [Ru(dmf)₃(IMesH₂)(?CH‐2‐(2‐PrO)‐C₆H₄)][(BF₄)₂] ( 1 ; IMesH₂=1,3‐dimesitylimidazolin‐2‐ylidene) has been prepared and used in continuous metathesis reactions by exploiting supported ionic‐liquid phase (SILP) technology. For these purposes, ring‐opening metathesis polymerization (ROMP)‐derived monoliths were prepared from norborn‐2‐ene, tris(norborn‐5‐ene‐2‐ylmethyloxy)methylsilane, and [RuCl₂(PCy₃)₂(CHPh)] (Cy=cyclohexyl) in the presence of 2‐propanol and toluene and surface grafted with norborn‐5‐en‐2‐ylmethyl‐N,N,N‐trimethylammonium tetrafluoroborate ([NBE‐CH₂‐NMe₃][BF₄]). Subsequent immobilization of the ionic liquid (IL), 1‐butyl‐2,3‐dimethylimidazolium tetrafluoroborate ([BDMIM][BF₄]), containing ionic catalyst 1 created the SILP catalyst. The use of a second liquid transport phase, which contained the substrate and was immiscible with the IL, allowed continuous metathesis reactions to be realized. High turnover numbers (TONs) of up to 3700 obtained in organic solvents for the ring‐closing metathesis (RCM) of, for example, N,N‐diallyltrifluoroacetamide, diethyl diallylmalonate, diethyl di(methallyl)malonate, tert‐butyl‐N,N‐diallylcarbamate, N,N‐diallylacetamide, diphenyldiallylsilane, and 1,7‐octadiene, as well as in the self‐metathesis of methyl oleate, could be further increased by using biphasic conditions with [BDMIM][BF₄]/heptane. Under continuous SILP conditions, TONs up to 900 were observed. Due to the ionic character of the initiator, catalyst leaching into the transport phase was very low (<0.1 %). Finally, the IL can, together with decomposed catalyst, be removed from the monolithic support by flushing with methanol. Upon reloading with [BDMIM][BF₄]/ 1 , the recycled support material again qualified for utilization in continuous metathesis reactions.     

离子液体-水介质中离子液体负载TEMPO催化选择氧化合成脂肪醇羟基芳香醛和酮

由于脂肪醇羟基和苄醇羟基具有相同的氧化反应活性,所以当分子内同时含有脂肪醇羟基和苄醇羟基时,很难选择氧化苄醇羟基合成含脂肪醇羟基的芳香醛或酮。本文报道了在离子液体-水介质中,NCS/NaBr/IL-TEMPO（离子液体负载TEMPO）催化氧化合成含有脂肪醇羟基的芳香醛、酮的方法,反应条件温和,选择性好,收率高,且离子液体和催化剂可以循环使用。     

Clean Procedure for the Synthesis of α-Aminophosphonates Catalyzed by Biodegradable Ionic Liquid

Abstract

A biodegradable SO₃H-functionalized ionic liquid (IL) was prepared and used as the catalyst for a one-pot, three-component condensation synthesis of α-aminophosphonates from aldehydes, amines, and triethylphosphite/diethylphosphite at room temperature under solvent-free conditions or in aqueous media. The products could be simply separated from the reaction mixture and the catalyst could be recycled and reused for several times without noticeably reducing catalytic activity.     

Palladium complex in a room temperature ionic liquid: a convenient recyclable reagent for catalytic oxidation

Palladium (Pd)-catalyzed carbonylation of alcohols proceeds in ionic liquid (IL) media (1-ethyl-3-methylimidazolium hexafluorophosphate). Carbonylation of primary/secondary alcohols to aldehydes/ketones was greatly accelerated by the use of a Pd-based catalyst in the presence of NaOCl as an oxidant. The catalyst was more easier to recycle in the IL [Emim]PF₆ with an equal-proportioned CH₂Cl₂ than in the single CH₂Cl₂ or IL.     

Biphasic ethylene polymerisation using ionic liquid over a titanocene catalyst activated by an alkyl aluminium compound

1-n-Butyl-3-methylimidazolium tetrachloroaluminate ([BMIM]⁺[AlCl₄]⁻) was applied to biphasic ionic liquid/hexane ethylene polymerisation as a medium of the Cp₂TiCl₂ titanocene catalyst activated by alkylaluminium compounds (MAO, AlEt₂Cl, AlEt₃). The best results were obtained using AlEt₂Cl. The results show that catalyst recycling, higher ethylene pressure, and greater Al/Ti molar ratio along with a greater volume of the ionic liquid phase enhance catalyst activity. The polyethylene gathered from the hexane phase is characterised primarily by its high purity. Its physical properties remain polyethylene obtained over a heterogeneous metallocene catalyst. Thus, biphasic ionic liquid polymerisation using a metallocene catalyst is possible and offers interesting technological implications.     

Effect of Cation Structure in Quinolinium-Based Ionic Liquids on the Solubility in Aromatic Sulfur Compounds or Heptane: Thermodynamic Study on Phase Diagrams

Experimental and theoretical studies on thermodynamic properties of quinolinium-based ionic liquids (ILs) based on bis(trifluoromethylsulfonyl)imide anion (namely N-butyl-quinoloinium bis(trifluoromethylsulfonyl)imide, [BQuin][NTf₂], N-hexylquinoloinium bis(trifluoromethyl-sulfonyl)imide, [HQuin][NTf₂], and N-octylquinoloinium bis(trifluoromethyl-sulfonyl)imide, [OQuin][NTf₂]) with aromatic sulfur compounds and heptane, as a model compound of fuel were examined in order to assess the applicability of the studied ionic liquids for desulfurization of fuels. With this aim, the temperature-composition phase diagrams of 13 binary mixtures composed of organic sulfur compounds (thiophene, benzothiophene, or 2-methylthiophene) or heptane and ionic liquid (IL) were investigated at ambient pressure. A dynamic method was used to determine the (solid–liquid) equilibrium phase diagrams in binary systems over a wide composition range and temperature range from T = 255.15 to 365.15 K up to the fusion temperature of ILs. The immiscibility gap with an upper critical solution temperature (UCST) was observed for each binary system under study. The influence of the alkane chain length of the substituent on the IL cation and of the sulfur compounds (the aromaticity of the solvent) was described. The experimental (solid + liquid) phase equilibrium dataset were successfully correlated using the well-known NRTL equation.     

Recycle and recovery of rhodium complexes with water-soluble and amphiphilic phosphines in ionic liquids for hydroformylation of 1-hexene

A biphasic catalysis system composed of ionic liquid and rhodium complexes with water-soluble or amphiphilic phosphine ligands bearing water-soluble groups of sodium sulfonate have been employed for hydroformylation of 1-hexene. The experimental results show that the activity is almost independent of the hydrotropicity of the phosphine ligands in BMI·BF₄. In this system, the extraction of phosphine species by the organics from the IL phase was quite low but larger than that of rhodium species and showed rather good stability of catalytic activity. A slight decrease in the aldehyde n/i ratio during the catalyst reuse could be recovered, in part, by replenishing certain amount of ligand into the used catalyst system.     

Magnetic carbon nanotube‐supported imidazolium cation‐based ionic liquid as a highly stable nanocatalyst for the synthesis of 2‐aminothiazoles

Magnetic carbon nanotube‐supported imidazolium ionic liquid (CNT‐Fe₃O₄‐IL) was synthesized and investigated using various characterization techniques, including Fourier transform infrared and Raman spectroscopies, X‐ray diffraction, vibrating sample magnetometry, scanning and transmission electron microscopies, and thermogravimetric and differential thermal analyses. In order to synthesize the CNT‐Fe₃O₄‐IL nanocomposites, Fe₃O₄‐decorated multi‐walled CNTs were modified with 1‐methyl‐3‐(3‐trimethoxysilylpropyl)‐1H‐imidazol‐3‐ium chloride. This catalytic system was found to be a highly stable, active, reusable and solid‐phase catalyst for the synthesis of 2‐aminothiazoles via the one‐pot reaction of ketone, thiourea and N‐bromosuccinimide under mild conditions. Immobilized magnetic ionic liquid catalysis combines the advantages of ionic liquid media with magnetic solid support nanomaterials which enables the application of nanotechnology and green chemistry in chemical processes. Copyright © 2016 John Wiley & Sons, Ltd.     

Understanding the Buoy Effect of Surface-Enriched Pt Complexes in Ionic Liquids: A Combined ARXPS and Pendant Drop Study**

Recently, we demonstrated that Pt catalyst complexes dissolved in the ionic liquid (IL) [C₄C₁Im][PF₆] can be deliberately enriched at the IL surface by introducing perfluorinated substituents, which act like buoys dragging the metal complex towards the surface. Herein, we extend our previous angle-resolved X-ray photoelectron spectroscopy (ARXPS) studies at complex concentrations between 30 and 5 %_mol down to 1 %_mol and present complementary surface tension pendant drop (PD) measurements under ultraclean vacuum conditions. This combination allows for connecting the microscopic information on the IL/gas interface derived from ARXPS with the macroscopic property surface tension. The surface enrichment of the Pt complexes is found to be most pronounced at 1 %_mol. It also displays a strong temperature dependence, which was not observed for 5 %_mol and above, where the surface is already saturated with the complex. The surface enrichment deduced from ARXPS is also reflected by the pronounced decrease in surface tension with increasing concentration of the catalyst. We furthermore observe by ARXPS and PD a much stronger surface affinity of the buoy-complex as compared to the free ligands in solution. Our results are highly interesting for an optimum design of IL-based catalyst systems with large contact areas to the surrounding reactant/product phase, such as in supported IL phase (SILP) catalysis.     

Reduction of Aldehydes and Ketones with Potassium Borohydride as Reductant

A series of aldehydes and ketones were reduced by potassium borohydride in an ionic liquid/water ([bmim]PF6/H2O) biphasic system to afford corresponding alcohol with high purity in excellent yields. The ionic liquid/water biphasic system could promote the chemoselectivity and the substituents such as nitro group and chlorine remained intact. Aromatic ketones were not as active as aromatic aldhydes and cyclic ketones owing to their higher steric hindrance. The ionic liquid could be recycled and reused. This protocol has notable advantages of no need of phase transfer catalyst and organic solvents, mild conditions, simple operation, short reaction time, ease work-up, high yields and recycling of the ionic liquid.     

Surfactant‐directed one‐pot preparation of novel Ti‐containing mesomaterial with improved catalytic activity and reusability

Titanium was incorporated in ionic liquid based periodic mesoporous organosilica to prepare a nanostructured catalyst (Ti@PMO‐IL) with high activity. Procedure for the synthesis of Ti@PMO‐IL was followed according the simultaneous hydrolysis and condensation of alkylimidazolium ionic liquid, tetramethoxysilane (TMOS) and tetrabutylorthotitanate (TBOT) where a surfactant template was used together with a simple acid‐based catalytic aproach. N₂ adsorption isotherm of the Ti@PMO‐IL was studied to measure its mean pore volume, pore size distribution and specific surface area. Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was applied to identify the chemical bonds present in Ti@PMO‐IL. The morphology of this nanomaterial was investigated by scanning electron microscopy (SEM). Transmission electron microscopy (TEM) image was used to study mesoporosity and structure order of the catalyst. The catalytic activity of Ti@PMO‐IL was then studied and found to be efficient and reusable to catalyze Hantzsch reaction.     

Selective Hydrogenation and Hydrodeoxygenation of Aromatic Ketones to Cyclohexane Derivatives Using a Rh@SILP Catalyst

Rhodium nanoparticles immobilized on an acid‐free triphenylphosphonium‐based supported ionic liquid phase (Rh@SILP(Ph₃‐P‐NTf₂)) enabled the selective hydrogenation and hydrodeoxygenation of aromatic ketones. The flexible molecular approach used to assemble the individual catalyst components (SiO₂, ionic liquid, nanoparticles) led to outstanding catalytic properties. In particular, intimate contact between the nanoparticles and the phosphonium ionic liquid is required for the deoxygenation reactivity. The Rh@SILP(Ph₃‐P‐NTf₂) catalyst was active for the hydrodeoxygenation of benzylic ketones under mild conditions, and the product distribution for non‐benzylic ketones was controlled with high selectivity between the hydrogenated (alcohol) and hydrodeoxygenated (alkane) products by adjusting the reaction temperature. The versatile Rh@SILP(Ph₃‐P‐NTf₂) catalyst opens the way to the production of a wide range of high‐value cyclohexane derivatives by the hydrogenation and/or hydrodeoxygenation of Friedel–Crafts acylation products and lignin‐derived aromatic ketones.     

Bimetallic Nanoparticles in Supported Ionic Liquid Phases as Multifunctional Catalysts for the Selective Hydrodeoxygenation of Aromatic Substrates

Bimetallic iron–ruthenium nanoparticles embedded in an acidic supported ionic liquid phase (FeRu@SILP+IL‐SO₃H) act as multifunctional catalysts for the selective hydrodeoxygenation of carbonyl groups in aromatic substrates. The catalyst material is assembled systematically from molecular components to combine the acid and metal sites that allow hydrogenolysis of the C=O bonds without hydrogenation of the aromatic ring. The resulting materials possess high activity and stability for the catalytic hydrodeoxygenation of C=O groups to CH₂ units in a variety of substituted aromatic ketones and, hence, provide an effective and benign alternative to traditional Clemmensen and Wolff–Kishner reductions, which require stoichiometric reagents. The molecular design of the FeRu@SILP+IL‐SO₃H materials opens a general approach to multifunctional catalytic systems (MM′@SILP+IL‐func).     

Co (II)‐C12 alkyl carbon chain multi‐functional ionic liquid immobilized on nano‐SiO2 nano‐SiO2@CoCl3‐C12IL as an efficient cooperative catalyst for C–H activation by direct acylation of aryl halides with aldehydes

Nano‐silica supported ionic liquids composed of alkyl carbon chain and transition metal chlorides anions have been prepared and successfully applied as a heterogeneous catalyst in the direct aldehyde C‐H activation. Catalytic results indicated that nano‐SiO₂ supported ionic liquid consisting C12 alkyl carbon chain and CoCl₃ anion nano‐SiO₂@CoCl₃‐C12IL showed excellent catalytic properties with good to excellent yields towards the desired aryl ketones. The excellent recyclability of the supported catalyst, mild reaction conditions, low catalyst loading, and operational simplicity are the important features of this methodology.     

Synthesis and characterization of MgO nanoparticles supported on ionic liquid‐based periodic mesoporous organosilica (MgO@PMO‐IL) as a highly efficient and reusable nanocatalyst for the synthesis of novel spirooxindole‐furan derivatives

The synthesis and catalytic application of a novel MgO containing periodic mesoporous organosilica with ionic liquid framework (MgO@PMO‐IL) is described. The prepared MgO@PMO‐IL was characterized by Fourier transform‐infrared spectroscopy, N₂ adsorption/desorption, transmission electron microscopy, field emission‐scanning electron microscopy, thermogravimetric and inductively coupled plasma analyses. This nanocatalyst was successfully applied as a highly efficient and recoverable catalyst for the synthesis of novel spirooxindole‐furan derivatives via the three‐component reaction of 1,3‐dicarbonyl compounds, N‐phenacyl pyridinium salts and isatin derivatives. The products were achieved in high to excellent yields with a simple work‐up procedure and short reaction times, and the catalyst could be recovered through a simple filtration process and successfully reused seven times without any significant decrease in its efficiency.     

Functional ionic liquid from biorenewable materials: synthesis and application as a catalyst in direct aldol reactions

A new room temperature ionic liquid (IL) (2-hydroxyethyl)-trimethyl-ammonium (S)-2-pyrrolidinecarboxylic acid salt ([Choline][Pro]) has been synthesized from biorenewable and nontoxic raw materials (choline chloride and l(−)-proline) in a simple and relative green route. The IL has been demonstrated to be the efficient catalyst of the direct aldol reactions between ketones and aromatic aldehydes in water at room temperature. The aldol products can be obtained with good yields and the IL in aqueous phase can be separated easily and reused.     

Selective separation of protein and saccharides by ionic liquids aqueous two-phase systems

In the present work, it was found that aqueous solution of a hydrophilic ionic liquid (IL), 1-butyl-3-methylimidazolium dicyanamide ([C₄mim][N(CN)₂]), could be separated into an aqueous two-phase system (ATPS) by inorganic salts such as K₂HPO₄ and K₃PO₄. The top phase is IL-rich, while the bottom phase is phosphate-rich. It was shown that 82.7%–100% bovine serum albumin (BSA) could be enriched into the top phase and almost quantitative saccharides (arabinose, glucose, sucrose, raffinose or dextran) were preferentially extracted into the bottom phase in a single-step extraction by [C₄mim][N(CN)₂] + K₂HPO₄ ATPS. The extraction efficiency of BSA from the aqueous saccharide solutions was influenced by the molecular structure of saccharides. The conductivity, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were combined to investigate the microstructure of the IL-rich top phase and the possible mechanism for the selective separation. It is suggested that the formation of the IL aggregate and the IL aggregate-BSA complex plays a significant role in the separation of BSA from aqueous saccharide solutions. This is the first example for the selective separation by ILs-based ATPSs. It is expected that these findings would have potential applications in bio-analysis, separation, and IL recycle.     

Characterization of Supported Ionic Liquid Phase (SILP) materials prepared from different supports

Supported ionic liquid phase (SILP) materials are a recent concept where a film of ionic liquid (IL) is immobilized on a solid phase, combining the advantages of ILs (non volatility, high solvent capacity, etc.) with those of heterogeneous support materials. In this work, new SILP materials were prepared using a series of supports with different porosity and chemical nature. An imidazolium-based IL, 1-methyl-3-octylimidazolium hexafluorophosphate (OmimPF₆), was confined at variable contents (5–60% w/w) in three different activated carbons (ACs), silica (SiO₂), alumina (Al₂O₃) and titania (TiO₂).     

Ordered Mesoporous Organosilica with Ionic‐Liquid Framework: An Efficient and Reusable Support for the Palladium‐Catalyzed Suzuki–Miyaura Coupling Reaction in Water

The preparation of a novel palladium‐supported periodic mesoporous organosilica based on alkylimidazolium ionic liquid (Pd@PMO‐IL) in which imidazoilium ionic liquid is uniformly distributed in the silica mesoporous framework is described. Both Pd@PMO‐IL and the parent PMO‐IL were characterized by N₂‐adsorption–desorption, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), TEM, and solid‐state NMR spectroscopy. We have demonstrated that Pd@PMO‐IL is an efficient and reusable catalyst for the Suzuki–Miyaura coupling reaction of various types of iodo‐, bromo‐, and even deactivated aryl chlorides in water. It was also found that although the PMO‐IL nanostructure acts as reservoir for soluble Pd species, it can also operate as a nanoscaffold to recapture the Pd nanoparticles into the mesochannels thus preventing extensive agglomeration of Pd. This observation might be attributed to the isolated ionic liquid units that effectively control the reaction mechanism by preventing Pd agglomeration and releasing and recapturing Pd nanoparticles during the reaction process. The catalyst can be recovered and reused for at least four reaction cycles without significant loss of activity.     

功能化离子液体为载体液相合成二氢吡啶酮衍生物

在微波辐照条件下, 以甲基咪唑、氯乙醇和四氟硼酸钠为原料制备了含羟基功能化离子液体1-(2-羟乙基)-3-甲基咪唑四氟硼酸盐([2-hydemim][BF₄]), 并以其为液态载体, 首先与乙酰乙酸乙酯反应, 得到的中间体再分别和Meldrum酸、醋酸铵以及各种芳香醛反应, 最后在温和的条件下用甲醇钠进行切割反应, 得到了一系列产率和纯度较高的3,4-二氢吡啶酮衍生物, 目标化合物不需要进一步的色谱纯化处理, 纯度为95%～98%, 产率为83%～93%. 回收得到的功能化离子液体可以重复套用至少6次也不影响其活性. 表明该方法是一种高效的3,4-二氢吡啶酮衍生物的组合化学合成方法.