Imidazolium Hydrogen Sulfate Research Articles

Dual Acidic Ionic Liquid Immobilized on α-Fe2O3–MCM-41 Magnetic Mesoporous Materials as the Hybrid Acidic Nanocatalyst for the Synthesis of Pyrimido[4,5-d]pyrimidine Derivatives

Magnetic α-Fe2O3–MCM-41 mesoporous material functionalized by dual acidic ionic liquid (DAIL) was prepared through a two-step approach as a novel powerful acidic catalyst which provides high ionic media for reactions, by means of post-surface grafting of the mesochannels of α-Fe2O3–MCM-41 materials with 3-sulfobutyl-1-(3-propyltrimethoxysilane)imidazolium hydrogen sulfate as DAIL. Mesoporous MCM-41 was simply packed on the surface of ferric oxide nanoparticles and DAIL was efficiently incorporated into the mesochannels of MCM-41 generating Lewis and Bronsted acidic sites. The catalyst was characterized by FT-IR, X-ray powder diffraction, HRTEM, vibrating sample magnetometer, X-ray energy diffraction spectra, thermogravimetric and differential thermal analyses, and N2 adsorption–desorption measurements. The synthesized hybrid acidic MCM-41 showed good catalytic performance in the one-pot synthesis of pyrimido[4,5-d]pyrimidine derivatives using 6-aminouracil, aldehyde, and urea or thiourea under solvent free conditions. Moreover, it was proved that under this condition, the use of such a hybrid material as a catalyst plays the role of rendering the reactions while neither the α-Fe2O3–MCM-41 nor the 3-methyl-1-(4-sulfonic acid)butylimidazolium hydrogen sulfate were able to promote this reaction.

Acidic ionic liquid as “quasi-homogeneous” catalyst for controllable synthesis of cellulose acetate

In this paper, we demonstrated that acidic ionic liquids (ILs) can be used as “quasi-homogeneous” catalysts for the efficient acetylation of cellulose. Unlike existing techniques that use large amount of ILs as solvent to dissolve and acetylate cellulose, a small amount of acidic ILs was used as catalyst in this study to overcome the low efficiency associated with relatively high viscosity and costs of ILs during homogeneous acetylation. Fully substituted cellulose acetate with a conversion of 88.8% was obtained by using only 9mol% IL 1-vinyl-3-(3-sulfopropyl) imidazolium hydrogen sulfate as catalyst, which is much higher than that of common commercialized solid acid catalysts. The degree of substitution and solubility of the obtained cellulose acetate can be facilely controlled by varying the concentration of ILs and reaction time. The dual function of swelling and catalyzing of acidic ILs for the acetylation of cellulose is responsible for the excellent catalytic performance.

Magnetic nanoparticles supported imidazolium-based ionic liquids as nanocatalyst in microwave-mediated solvent-free Biginelli reaction

The magnetic Fe3O4 nanoparticles supported imidazolium-based ionic liquids (MNPs–IILs), namely 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium hydrogen sulfate (MNPs–IIL–HSO4), 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium acetate (MNPs–IIL–OAc) and 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium chloride (MNPs–IIL–Cl) were used as efficient new catalysts for the one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones under microwave irradiation and solvent-free conditions in excellent yields. Utilization of easy reaction conditions, catalyst with high catalytic activity and good reusability, and simple magnetically work-up, makes this green protocol as an interesting option for the economic synthesis of Biginelli compounds. Microwave technology as an eco-friendly green synthetic approach has gradually been used in this organic procedure. Combining the advantages of microwave irradiation and magnetically nanocatalyst, this method provides an efficient and much improved modification of the original Biginelli reaction. We believe that this procedure appears to have a broad scope with respect to variation in the 3,4-dihydropyrimidin-2(1H)-ones (thiones). we have developed a rapid, effective, validated and environmental-friendly method for the synthesis of dihydropyrimidinones (thiones) using Fe3O4 nanoparticles immobilized imidazolium salt catalyst in microwave irradiation and solvent-free conditions. Reduced reaction times, high turnover frequency, high yields of products, absence of solvent and recyclability of catalyst make our catalyst a valuable system addition to previously reported methods. This green methodology should be amenable to construct new substituted dihydropyrimidinones scaffolds with potential biological applications.

Four-component one-pot synthesis of unsymmetrical polyhydroquinoline derivatives using 3-methyl-1-sulfonic acid imidazolium hydrogen sulfate as a catalyst

3-Methyl-1-sulfonic acid imidazolium hydrogen sulfate has been used as an efficient, halogen-free, and reusable Brönsted acidic ionic liquid catalyst for the synthesis of ethyl-4-aryl/heteryl-hexahydro-trimehtyl-5-oxoquinoline-3-carboxylates via the one-pot condensation of dimedone with aryl/heteryl aldehydes, ethyl acetoacetate, and ammonium acetate under solvent-free conditions. This method has the advantage of being clean and simple, as well as providing the desired product in high yield over a short reaction time. Furthermore, the catalyst could be recycled and reused four times without any discernible reduction in activity.

ChemInform Abstract: One‐Pot Synthesis of Various Xanthene Derivatives Using Ionic Liquid 1,3‐Disulfonic Acid Imidazolium Hydrogen Sulfate as an Efficient and Reusable Catalyst under Solvent‐Free Conditions.

Abstract In this study, 1,3-disulfonic acid imidazolium hydrogen sulfate (DSIMHS) is used as an efficient and reusable ionic liquid for the green, mild, and efficient synthesis of xanthenes under solvent-free conditions. Simple and easy work-up, low cost, green process, short reaction times and excellent yields of the products are the advantages of this procedure. Further, the catalyst can be recycled and reused at least for four times without a noticeably decrease in its catalytic activity.

A solvent-free synthesis of coumarins using 1,3-disulfonic acid imidazolium hydrogen sulfate as a reusable and effective ionic liquid catalyst

1,3-Disulfonic acid imidazolium hydrogen sulfate has been used as an effective and reusable ionic liquid catalyst for the synthesis of coumarins from phenol derivatives with β-ketoesters via the Von Pechmann condensation under solvent-free conditions. This method consistently has the advantages of excellent yields, easy and quick isolation of the products, short reaction times, and green aspects by avoiding toxic catalysts and solvents. Further, the catalyst can be recovered and reused for four times without loss of activity.

ChemInform Abstract: Broensted Acidic Ionic Liquid Based Magnetic Nanoparticles: A New Promoter for the Biginelli Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones/thiones.

AbstractA Broensted acidic ionic liquid imidazolium hydrogen sulfate immobilized on magnetic Fe3O4 nanoparticles exhibits excellent catalytic activity in the Biginelli‐type synthesis of a diverse range of pyrimidine derivatives (IV).

Effect of Cation on Proton Conductivity of a Non-fluorinated Ionic Liquid

1-Ethyl-3-methyl imidazolium hydrogensulfate (EMIHSO4), a non-fluorinated IL, was studied both as liquid and polymer electrolytes for electrochemical capacitors [1]. While EMIHSO4exhibited a reasonable ionic conductivity, improvement in proton conductivity is possible by altering the structure of the cation, which warrants further investigation. The objectives of this study are twofold: to investigate the effect of cationic functional groups on the properties of the IL; and to select and characterize the IL system with optimum proton conductivity. The electrolytes were prepared using ILs with different cations, namely 1-ethyl-3-methyl imidazolium hydrogensulfate (EMIHSO4), 1-methylimidazolium hydrogensulfate (MIHSO4), and imidazolium hydrogensulfate (ImHSO4) in methanol solutions. For comparison, a solution of EMIHSO4 with propylene carbonate (PC), an aprotic solvent, was prepared with the same concentration as those in methanol-based electrolytes. To demonstrate the proton conductivity of the electrolytes, standard two-electrode cells were assembled utilizing pseudocapacitive electrodes such as RuO2and nanocarbon/polyoxometalate (POMs) composites [2].The cell performance were characterized using cyclic voltammtery (CV) and ac impedance spectroscopy. RuO2 exhibits pseudocapacitance via a coupled proton–electron transfer in a protic electrolyte. Figure 1 shows the CV profiles of the RuO2-based cells in all electrolytes. The ImHSO4 and MIHSO4-based cells demonstrated similar CVs and the highest capacitance performance. Their higher capacitance compared to EMIHSO4-based cell indicates the higher proton conductivity of ImHSO4 and MIHSO4, which can contribute to the electrochemical reactions of RuO2 electrodes. Due to the role of solvent on proton dissociation, the cell performance was superior using EMIHSO4/MeOH electrolytes than that for EMIHSO4/PC. The proton conductivity of PILs was further examined on a carbon/POM electrode and compared to the bare carbon electrodes. POMs involve fast and reversible multielectron transfer reactions in proton containing electrolytes. For a better comparison, the respective carbon/POM cells were also tested in 0.5M H2SO4. The electrochemical performance of the carbon/POM-based cells in the PIL electrolytes followed a similar trend as those for RuO2-based electrolytes. Figure 2 (a) shows the CV profiles of the carbon/POM-based cells and the bare carbon in ImHSO4/MeOH electrolyte. The increased capacitance of the carbon/POM cell over that for the bare carbon implies the proton conducting characteristic of ImHSO4 electrolyte which participates in the redox reaction of the POM. Figure 2 (b) presents the capacitance ratio of the carbon/POM cells in the respective PILs to H2SO4 electrolyte. ImHSO4-based cells showed the highest capacitance ratio followed by MIHSO4 and EMIHSO4in both MeOH and PC solutions. Imidazoles consist of two nitrogen sites, and their protonated and unprotonated nitrogen functions may act as proton donor and acceptor in proton transfer reactions. As the nitrogen sites decrease in MI and EMI cations, the contribution from proton conduction becomes smaller. More details on optimizing the proton conductivity of these PILs for room temperature applications, especially polymer electrolytes will be presented.

Solvent-free synthesis of quinoline derivatives via the Friedländer reaction using 1,3-disulfonic acid imidazolium hydrogen sulfate as an efficient and recyclable ionic liquid catalyst

Abstract A convenient, highly versatile and eco-friendly protocol for the synthesis of quinoline derivatives via the Friedlander reaction is presented. The method is based on the use of 1,3-disulfonic acid imidazolium hydrogen sulfate (DSIMHS) as an efficient and reusable ionic liquid catalyst. A variety of ketones afforded the substituted quinolines in excellent yields during relatively short reaction times under solvent-free conditions; the catalyst could be easily recovered and reused for several times without any appreciable loss of activity.

Brønsted Acidic Ionic Liquid Modified Magnetic Nanoparticle: An Efficient and Green Catalyst for Biodiesel Production

Surface-functionalized magnetic nanoparticle supported dual Bronsted acidic ionic liquid was synthesized by immobilizing 1-(propyl-3-sulfonate) imidazolium hydrogen sulfate [SO3H-(CH2)3-HIM][HSO4] onto the surface of Fe3O4@SiO2 using 3-chloropropyltrimethoxysilane as the “linker”. The structure of the catalyst was characterized by XRD, FT-IR, SEM, TEM, and VSM. The results demonstrated that the Fe3O4 particle was well retained in the silica matrix, presenting a core–shell structure with strong magnetic responsiveness. Meanwhile, the ionic liquid was successfully immobilized on the support. The as-prepared catalyst could disperse well in the reactants and showed good performance in esterification of oleic acid with short-chain alcohols and transesterification of soybean oil. Moreover, the catalyst could be easily separated from products by additional magnetic force without obvious mass loss and maintain satisfactory catalytic activity after being recycled eight times.

Brønsted acidic ionic liquid based magnetic nanoparticles: a new promoter for the Biginelli synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones

The Bronsted acidic ionic liquid 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium hydrogen sulfate was immobilized on magnetic Fe3O4 nanoparticles (MNPs-IL-HSO4). The properties of the magnetic nanocatalyst were characterized by FT-IR, EDX, SEM, elemental analysis, XRD, VSM, and TGA. The results showed that the ionic liquid had been successfully immobilized onto the magnetic support, and the immobilized ionic liquid catalysts exhibited high catalytic activity in the Biginelli reaction under mild conditions for the synthesis of a diverse range of 3,4-dihydropyrimidin-2(1H)-ones. It also maintained satisfactory catalytic activity for the synthesis of Biginelli compounds after 8 rounds of recycling. The separation and reuse of the novel solid catalyst were simple, effective and economical.

Biodiesel from Citrullus colocynthis oil: sulfonic-ionic liquid-catalyzed esterification of a two-step process.

Biodiesel was prepared from Citrullus colocynthis oil (CCO) via a two-step process. The first esterification step was explored in two ionic liquids (ILs) with 1,3-disulfonic acid imidazolium hydrogen sulfate (DSIMHSO4) and 3-methyl-1-sulfonic acid imidazolium hydrogen sulfate (MSIMHSO4). Both ILs appeared to be good candidates to replace hazardous acidic catalyst due to their exceptional properties. However, the two sulfonic chains existing in DSIMHSO4 were found to increase the acidity to the IL than the single sulfonic chain in MSIMHSO4. Based on the results, 3.6 wt% of DSIMHSO4, methanol/CCO molar ratio of 12 : 1, and 150°C offered a final FFA conversion of 95.4% within 105 min. A 98.2% was produced via second KOH-catalyzed step in 1.0%, 6 : 1 molar ratio, 600 rpm, and 60°C for 50 min. This new two-step catalyzed process could solve the corrosion and environmental problems associated with the current acidic catalysts.

One-pot synthesis of various xanthene derivatives using ionic liquid 1,3-disulfonic acid imidazolium hydrogen sulfate as an efficient and reusable catalyst under solvent-free conditions

Abstract In this study, 1,3-disulfonic acid imidazolium hydrogen sulfate (DSIMHS) is used as an efficient and reusable ionic liquid for the green, mild, and efficient synthesis of xanthenes under solvent-free conditions. Simple and easy work-up, low cost, green process, short reaction times and excellent yields of the products are the advantages of this procedure. Further, the catalyst can be recycled and reused at least for four times without a noticeably decrease in its catalytic activity.

Evaluation of catalytic activity of two functionalized imidazolium ionic liquids for biodiesel fuel production by a two-stage process

BACKGROUND Today commercial biodiesel processes use mainly homogeneous alkali catalysts when the feedstock is from refined oil with low FFA content. However, acidic catalysts become important when dealing with cheap feedstock that contains high amounts of FFA (>0.5%), such as crude oils and waste oils. Unfortunately, acid catalyst requires extensive and expensive purification steps for recovery from the valuable esters. Hence this study investigated the production of biodiesel from crude palm oil (CPO) containing high FFA content by a two-stage ionic liquid–KOH catalyzed process. To evaluate their catalytic activities, two functionalized imidazolium ionic liquids (ILs) with different anions were tested for esterifying the FFA. RESULTS Among the ILs investigated, 1-butyl-3-(3-sulfopropyl)-imidazolium hydrogensulfate (BSPIMHSO4) was found to be the better catalyst. Based on the experimental results, a BSPIMHSO4 concentration of 4.0 wt%, methanol:CPO molar ratio of 12:1, temperature of 150°C, and agitation speed of 600 rpm offered FFA conversion of 95.7% within 2 h. In the second step, at optimum conditions of 6:1 mole ratio of methanol:esterified CPO, 60°C, 600 rpm and 50 min; 1.0 wt% of KOH was used a catalyst for the transesterification reaction. The results obtained showed that the properties of synthesized biodiesel conform with the international standard specifications. CONCLUSION To understand the catalytic behavior of the IL during biodiesel synthesis, the effect of ionic liquid on the kinetics of esterification catalysis needs to be considered. © 2013 Society of Chemical Industry

Effects of ionic liquid mixtures on lipid extraction from Chlorella vulgaris

In this study, pre-biodiesel-production lipid extraction from microalgae (Chlorella vulgaris) was performed. The yield-enhancing effects of ionic liquid blends on the lipid extraction were investigated. The initial fatty acids content of the C. vulgaris was 292.2 mg/g cell. The lipid extraction yield using single ionic liquids was compared with the yield obtained with organic solvents and ionic liquid mixtures, respectively. The yield by hexane–methanol solvent was 185.4 mg/g cell. Among the 12 ionic liquids, 1-ethyl-3-methyl imidazolium acetate, 1-ethyl-3-methyl imidazolium diethylphosphate, 1-ethyl-3-methyl imidazolium tetrafluoroborate, and 1-ethyl-3-methyl imidazolium chloride showed high (>200.0 mg/g cell) lipid extraction yields. Although the yields of 1-ethyl-3-methyl imidazolium ethyl sulfate and 1-ethyl-3-methyl imidazolium thiocyanate were only 60.5 and 42.7 mg/g cell, respectively, the yield for their mixture (weight ratio of 1:1) was improved to 158.2 mg/g cell. Similarly, whereas the lipid extraction yield of 1-ethyl-3-methyl imidazolium hydrogen sulfate was just 35.2 mg/g cell, that for its mixture with 1-ethyl-3-methyl imidazolium thiocyanate (weight ratio of 1:1) was boosted to 200.6 mg/g cell. Overall, the synergistic effects of the ionic liquid mixtures with different anions improved the lipid extraction yield of C. vulgaris.

Esterification of fatty acids by new ionic liquids as acid catalysts

Three new highly acidic ionic liquids based on 4-sulfobenzyl imidazolium hydrogensulfate and with different length of the alkyl chain were screened as catalysts for the esterification of oleic acid with methanol. The ionic liquids were characterized by FT-IR, 1H NMR, 13C NMR and CHNS analyses. The reaction parameters, such as reaction temperature, molar ratio, catalyst loading, reaction time and stability were studied. The experimental results indicated that acidic ionic liquid with the longest alkyl chain performed the best activity, due to the less strict hindrance. Finally, the methyl oleate was produced with 95.0% yield at lower time (6h) under the optimized reaction conditions. Furthermore, different alcohols and fatty acids were investigated and the results showed that the length of alkyl chain and degree of saturation of fatty acid affects the catalytic activity of the best catalyst.

Preparation ofCitrullus colocynthis biodiesel via dual-step catalyzed process using functionalized imidazolium and pyrazolium ionic liquids for esterification step

In this research, dual step catalyzed process was implemented to prepare biodiesel from crude Citrullus colocynthis oil (CCO). Two ionic liquids (ILs) were synthesized and evaluated as pre-catalyst for the FFA-esterification first step. A 1-methyl-3-(4-sulfobutyl)-imidazolium hydrogensulfate (MSBIMHSO4) showed a higher FFA conversion than the pyrazolium IL of 1-methyl-2-(4-sulfobutyl)-pyrazolium hydrogensulfate (MSBPHSO4). A 96.7% FFA conversion was achieved at the optimal conditions of 3.8wt% of MSBIMHSO4, molar ratio of 12:1 methanol:CCO, 130°C, and 600rpm agitation rate for 2h. In the second step, KOH-transesterification reaction of the esterified CCO was performed at 60°C, 6:1 mole ratio of methanol:oil, and 600rpm in a reaction system containing 1.0wt% of catalyst for 50min. The final yield in 98.8% revealed that the process proposed for novel CCO in this study led to a tolerable biodiesel, meeting the ASTM requirements for its utilization as a fuel. Furthermore, this new dual step catalyzed process could solve the old homogeneous-catalyzed processes drawbacks.

Synthesis of 10-aryl-7,9-dihydro-3H-furo[3,4-b]pyrazolo[4,3-f]quinolin-9-one using supported ionic liquid

A series of 3H-furo[3,4-b]pyrazolo[4,3-f]quinolinone derivatives has been synthesized through three-component reaction of tetronic acid, 5-aminoindazole and various aromatic aldehydes in the presence of the silica-supported ionic liquid 1-methyl-3-(triethoxysilylpropyl)imidazolium hydrogen sulfate as the catalyst.

High Rate Performance of Flexible Pseudocapacitors fabricated using Ionic-Liquid-Based Proton Conducting Polymer Electrolyte with Poly(3, 4-ethylenedioxythiophene):Poly(styrene sulfonate) and Its Hydrous Ruthenium Oxide Composite Electrodes

We report the studies on all-solid-state flexible pseudocapacitors based on poly (3,4-ethylenedioxythiophene)-poly (styrene sulfonate) (PEDOT-PSS) and PEDOT-PSS/hydrous ruthenium oxide composite electrodes separated by nonaqueous proton conducting polymer electrolyte. Structural, thermal and electrochemical properties including high ionic conductivity (6.2 × 10(-2) S cm(-1) at 20 °C) of the polymer electrolyte, comprising ionic liquid 1-ethyl 3-methyl imidazolium hydrogen sulfate (EMIHSO4) immobilized in the blend of poly (vinyl alcohol) (PVA) and poly (vinyl pyrrolidone) (PVP), demonstrate its excellent suitability in supercapacitor fabrication. A substantial improvement in the specific capacitance (hence the specific energy) has been obtained when the PEDOT-PSS electrodes in the symmetrical pseudocapacitor are replaced by the composite electrodes PEDOT-PSS/RuO2·xH2O. High rate capability of the capacitor cell (with PEDOT-PSS electrodes) has been observed, as evidenced from the high knee frequency (∼966 Hz), low response time (∼70 ms) and high pulse power (∼10.2 kW kg(-1)), observed by impedance analysis. Almost rectangular (capacitive) cyclic voltammetric patterns for high scan rates (up to 15 V s(-1)) confirm the high rate performance of the pseudocapacitor. The PEDOT-PSS/RuO2·xH2O composite electrodes show the lower rate capability (knee frequency ∼312 Hz, response time ∼1 s, pulse power ∼3.2 kW kg(-1) and capacitive CV response up to 500 mV s(-1)) because of slow exchange of charges at the interfaces via RuO2·xH2O. However, the pseudocapacitor with composite electrodes shows higher rate performance relative to many reported RuO2·xH2O systems. About 15% improvement is noticed in the capacitance value when the capacitor with composite electrodes is initially charged and discharged up to ∼200 cycles. Thereafter, the cell shows almost constant value of specific capacitance (∼70 F g(-1)) for 1000 cycles.

Ionic Liquid Mediated Synthesis of Novel tetrahydroimidazo [1,2- a]pyrimidine-6-carboxylate Derivatives

Abstract: A novel route for the synthesis of tetrahydroimidazo [1,2-a] pyrimidine-6-carboxylate derivatives in presence of 1-ethyl-3-methyl imidazolium hydrogen sulphate ionic liquid at room temperature has been reported via Biginelli reac-tion. The process offer several advantages such as short reaction time, excellent yield of products, simple work up proce-dure etc. 1-ethyl-3-methyl imidazolium hydrogen sulphate ionic liquid is utilized as solvent system and catalyst to en-hance the rate of reactions. Keywords: Aromatic aldehydes, Biginelli reaction, Catalyst, Ionic liquid, 5-amino-4,5-dihydro-1 H -pyrazole-4-carbonitrile. INTRODUCTION 3, 4-Dihydropyrimidine-2-(1 H )-ones and their deriva-tives are pharmacologically important because of having several potential biological activities including, antiviral, antibacterial, antitumor and antihypertensive agents. Fur-thermore, these compounds have emerged as the integral backbone of certain calcium channel blockers [1 - 6]. Recently to improve and modify the process, various syn-thetic methodologies for the preparation of such compounds have been developed using microwave irradiation [7-11], by using Lewis and Bronsted acids FeCl