Bronsted Acidic Ionic Liquids Research Articles

Novel Brønsted Acidic Ionic Liquid ([CMIM][CF3COO]) Prompted Multicomponent Hantzsch Reaction for the Eco-Friendly Synthesis of Acridinediones: An Efficient and Recyclable Catalyst

A novel, highly efficient and recyclable Bronsted acidic ionic liquid ([CMIM][CF3COO]) has been successfully implemented for the synthesis of acridinediones in aqueous media. Recyclability of novel catalyst, high yields, use of environmentally benign aqueous media as solvent, simple product isolation, high atom economy and sidestep to column chromatography are the noteworthy features of this protocol. This protocol is competent for producing wide library of acridinediones in good to excellent yields. Furthermore, molecular structure and relative stereochemistry of 4c and 4s derivatives were confirmed by single-crystal X-ray diffraction.

Synthesis and Thermophysical Properties of Imidazolium-Based Bronsted Acidic Ionic Liquids

A range of imidazolium-based Bronsted acidic ionic liquids (ILs) have been synthesized by varying the side chain length of the alkyl and alkyl sulfonic group incorporated to the C1 and C3 positions in the imidazolium ring respectively with a fixed HSO4– anion. The synthesized ILs were characterized using NMR for structure confirmation and CHNS for elemental analysis. The thermal properties such as thermal decomposition temperature were determined using thermogravimetric analysis, and several key physical properties such as viscosity and density were measured within a temperature range of 20 °C to 80 °C using an Anton Paar viscometer and densitometer. The density measurement results and established equations were used to calculate the molecular volumes, standard entropies, crystal lattice energies, and thermal expansion coefficients of the synthesized ILs.

A convenient approach for the synthesis of 1,3,5-trioxanes under solvent-free conditions at room temperature

A series of environmentally benign bis-SO3H-functionalized Bronsted acidic ionic liquids were synthesized by using aliphatic polyamines and 1,3-propanesultone as the source chemicals. These ionic liquids acted as efficient inexpensive and recyclable catalysts for cyclotrimerization of aliphatic aldehydes at room temperature under solvent-free conditions. The reactions proceeded smoothly with good to excellent isolated yields (66.9–97.6 %=) and were generally complete in 1.5 h when the amount of ionic liquids was 0.1 mol%. The ionic liquids could be recovered readily and reused five times without any significant loss in their catalytic activity.

Facile synthesis of fructone from ethyl acetoacetate and ethylene glycol catalyzed by SO3H-functionalized Brønsted acidic ionic liquids

SO3H-functionalized Brønsted acidic ionic liquids (BAILs) were synthesized and utilized as highly efficient catalysts for the production of fructone via the acetalization reaction of ethyl acetoacetate with ethylene glycol. In comparison with conventional H2SO4 and cation exchange resins, the BAILs N-(4-sulfonic acid) butyl triethylammonium hydrogensulfate ([BSEt3N][HSO4]) of strong acidities exhibited excellent catalytic activities. The effects of various parameters such as different BAILs, reaction temperature, catalyst dosage, and molar ratio of the reactants on the conversion of ethyl acetoacetate were investigated in detail. The experimental results indicated that the catalytic performance of BAILs were closely related to their Hammett acidities. Moreover, it was found that [BSEt3N][HSO4] could be also recovered easily and used repetitively six times without obvious decline in activity and quantity, showing great potential application in industry.

SO3H-functionalized Brønsted acidic ionic liquids as efficient catalysts for the synthesis of isoamyl salicylate

Six Brønsted acidic ionic liquids (BAILs) composed of [HSO4] were prepared, characterized, and used as catalysts of low dosage in the synthesis of isoamyl salicylate.

Pd-catalyzed ethylene methoxycarbonylation with Brønsted acid ionic liquids as promoter and phase-separable reaction media

Bronsted acid ionic liquids (BAILs) were prepared and applied as combined acid promoters and reaction media in Pd–phosphine catalyzed methoxycarbonylation of ethylene to produce methyl propionate. The BAILs served as alternatives to common mineral acids required for the reaction, e.g. methanesulfonic acid or sulfuric acid, resulting in high catalytic activity and selectivity towards methyl propionate. In addition, the BAILs yielded a biphasic system with the product and provided stability to palladium intermediates avoiding the undesirable formation of palladium black after reaction. These special features enabled facile methyl propionate separation and recovery of the ionic liquid catalyst system, thus allowing its re-use up to 15 times without apparent loss of catalytic activity or selectivity.

Synthesis of a 3D-network polymer supported Bronsted acid ionic liquid based on calix[4]resorcinarene via two post-functionalization steps: a highly efficient and recyclable acid catalyst for the preparation of symmetrical bisamides

We report a straightforward route for the synthesis of a novel functional polymer bearing ionic liquid as an efficient and green acidic catalyst for the preparation of bisamides.

Single reactor conversion of corn stover biomass to C5–C20 furanic biocrude oil using sulfonic acid functionalized Brönsted acidic ionic liquid catalysts

Cellulose (DP∼450) and dry corn stover powder were converted to furanic biocrude oils in a single reactor operation by heating with excess acetone in the presence of Bronsted acidic ionic liquid catalysts. Two Bronsted acidic ionic liquid catalysts, 1-(1-propylsulfonic)-3-methylimidazolium chloride (BAIL-1) and 1-(4-sulfonic-benzyl)-3-methylimidazolium chloride (BAIL-2), were compared for biocrude oil synthesis from cellulose and dry corn stover. Catalyst BAIL-1 showed slightly better activity in all experiments, where cellulose samples produced 52.9 mg biocrude oil/100 mg of cellulose, and corn stover produced 34.2 mg biocrude oil/100 mg of corn stover by heating at 120 °C for 3 h. Biocrude oil formed in the novel process is mainly a complex mixture of aldol condensation products of acetone with biomass-derived furans, furfural and 5-hydroxymethylfurfural.

Liquid phase catalytic dehydration of glycerol to acrolein over Brønsted acidic ionic liquid catalysts

Liquid phase dehydration of glycerol to acrolein catalyzed by Brønsted acidic ionic liquids (BAILs) using semi-batch reaction technique was investigated. For the BAILs catalysts, the acrolein yields were in an order of [Bmim]H2PO4>[Bmim]HSO4>[BPy]HSO4>[PSPy]HSO4>[N2224]HSO4>[PSPy]H2PO4>[BPy]H2PO4>[N2224]H2PO4. When [Bmim]H2PO4 and [Bmim]HSO4 were used as the catalysts at 270°C with the molar ratio of catalyst to glycerol of 1:100, the acrolein yields were 57.4% and 50.8%, respectively, at complete conversion of glycerol. The BAILs with [Bmim] cation and moderate acidity favored the formation of acrolein in liquid phase glycerol dehydration.

Efficient synthesis of 1-carbamatoalkyl-2-naphthols using Brønsted acidic ionic liquid as reusable catalyst

Efficient synthesis of 1-carbamatoalkyl-2-naphthols can be carried out in the presence of halogen-free Bronsted acidic ionic liquid, synthesized from 1,4-diaza-bicyclo[2.2.2]octane (DABCO) and 1,4-butanesulfonate. A wide range of aldehydes and carbamates easily undergo condensation with 2-naphthol to afford the desired products in good to excellent yields. The present methodology offers several advantages, such as a simple work-up procedure and short reaction times. The catalyst can be recycled and reused without substantial reduction in catalytic activities.

Brønsted acidic ionic liquids catalyzed the preparation of 13-aryl-5H-dibenzo[b,i]xanthene-5,7,12,14(13H)-tetraones and 3,4-dihydro-1H-benzo[b]xanthene-1,6,11(2H,12H)-triones

An environmentally green method for the synthesis of 13-aryl-5H-dibenzo[b,i]xanthene-5,7,12,14(13H)-tetraone and 3,4-dihydro-1H-benzo[b]xanthene-1,6,11(2H,12H)-trione derivatives using Bronsted acidic ionic liquids, 3-methyl-1-sulfonic acid imidazolium chloride, 1-H-3-methyl-imidazolium hydrogensulfate, triethylamine-bonded sulfonic acid, and triethylammonium hydrogensulfate as reusable catalysts under thermal solvent-free conditions is described.

Brønsted acidic ionic liquids catalyze the high-yield production of diphenolic acid/esters from renewable levulinic acid

The high-yielding synthesis of diphenolic acid (DPA) using Bronsted acidic ionic liquids (BAILs) has been demonstrated in this study. Importantly, p,p′-DPA was obtained as the preferential product over o,p′-DPA with an isomer ratio over 100. Moreover, diphenolic esters were also prepared in high yield through a one-pot method.

Synthesis of linear and hyperbranched polyesters in Brønsted acid ionic liquids

Imidazolium based Bronsted acid ionic liquids (BAILs) were proved to be very efficient solvents and catalysts for linear and hyperbranched polyester synthesis. Linear polyesters of diols and diacids with mass-average molar mass (Mw) up to 36 000 g mol−1 were obtained by the post-polycondensation of low molar-mass oligoesters at 110 °C in 15–30 min. Hyperbranched polyesters of 2,2-bis(hydroxymethyl)propanoic acid with a Mw of ca. 10 000 g mol−1 were yielded in 3-butyl-1-(butyl-4′-sulfonic acid)imidazolium hydrogen sulfate ([BBSIm]HSO4) in no more than 2 h, which is considerably shorter than the conventional polyesterification in the bulk. The degree of branching of the resulting hyperbranched polyesters increased with time. [BBSIm]HSO4 was found to be more suitable for polyesterification, as only the expected polyester was produced, while when polycondensations were carried out in the BAIL with Tf2N− anion ([BBSIm]Tf2N), side reactions were observed: ether formation and polymer scissions in linear polyester synthesis, and gelation in hyperbranched polyesterification.

Symmetrical and unsymmetrical Brønsted acidic ionic liquids for the effective conversion of fructose to 5-hydroxymethyl furfural

Symmetrical and unsymmetrical Bronsted acidic Ionic Liquids (ILs) have been synthesized via a one-pot halogen-free route and characterized by TGA-DTA and DSC to compare their stability and activity. The acidities of the four ILs have also been tested by the Hammett method. These ILs were utilised as catalysts for the dehydration of fructose to 5-hydroxymethylfurfural (HMF) in the presence of dimethylsulphoxide (DMSO) as solvent. The effects of reaction time, temperature and catalyst concentration were studied. The ILs are very efficient for the reaction at relatively lower temperature with very good HMF yield and selectivities. The used ILs could be easily recycled without any significant loss in fructose conversion and HMF yield.

Study of Preparation and Thermal Stability of Cyano-Functionalized Imidazolium Type Ionic Liquids

Sixteen imidazolium type cyano-functionalized Bronsted acidic ionic liquids with HSO 4 - and H 2 PO 4 - anion were prepared adopting two-step method and were characterized by FT-IR, 1 H and 13 C NMR. The onset temperatures of thermal decomposition of the ionic liquids were measured using thermogravimetric analysis. It was found that the decomposition onset temperatures of the as-synthesized ionic liquids were in the range of 200-260 ℃. Additionally, the decomposition temperatures were highly dependent on the nature of the anions. Thermal stability of these cyano-functionalized ionic liquids decreased in the order of HSO 4 - > H 2 PO 4 - .

Biodiesel synthesis from the esterification of free fatty acids and alcohol catalyzed by long-chain Brønsted acid ionic liquid

A long-chain Bronsted acid ionic liquid (IL), 3-(N,N-dimethyldodecylammonium)propanesulfonic acid p-toluenesulfonate ([DDPA][Tos]), was prepared and characterized by FT-IR, 1H NMR, 13C NMR, UV/vis and TGA. The H0 (Hammett function) value of the IL was also determined. The IL as catalyst was applied to the catalytic synthesis of biodiesel from free fatty acids (FFAs). The influencing factors, such as the type and amount of catalyst, reaction time, molar ratio of fatty acid to methanol and reaction temperature, were investigated. The results indicated that the long-chain Bronsted acid IL showed high catalytic activity and fair reusability. Esterification was accomplished under the following optimized conditions: molar ratio of alcohols to FFA at 1.5 : 1, mole fraction of ionic liquid at 10%, 60 °C, and 3 h. The products could be separated from the catalyst system by liquid–liquid biphase separation at room temperature with good yields of 92.5% to 96.5%. The catalyst could be reused nine times after the removal of water and alcohol. Therefore, the long-chain Bronsted acid IL has good potential for the synthesis of biodiesel from low-cost feedstocks such as waste oil and woody plant oils.

Kinetics Study of the Ketalization Reaction of Cyclohexanone with Glycol Using Brønsted Acidic Ionic Liquids as Catalysts

It is remarkable that Bronsted acidic ionic liquids (BAILs) have several unique advantages in the acid-catalysis reaction, which avoids the technical issues raised from mineral acids. The kinetics for the ketalization of cyclohexanone with glycol using BAILs as catalysts was therefore studied for the first time. The effects of various parameters such as kind of BAILs, temperature, catalyst loading, and molar ratio of the reactants on the conversion of cyclohexanone were examined in detail, and a pseudohomogeneous (PH) kinetic model was used successfully to correlate the experimental data in the temperature range from 313.15 to 343.15 K. The kinetic parameters such as reaction rate constant, activation energy, and chemical equilibrium constant then were proposed and utilized to interpret the catalytic activities of the BAILs catalysts. It was also validated from the comparison of catalytic performance among the BAILs, H2SO4, and solid resin that the BAILs were considered to be environmentally friendly and ...

Solubility of CO2 in amide-based Brønsted acidic ionic liquids

Several hydrophilic amide-based Brønsted acidic ionic liquids (BAILs) were prepared by simple acid-base neutralization reaction of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP) with trifluoroacetic acid (TFA) or tetrafluoroboric acid (FBA). The solubility data of CO2 in these BAILs were determined at T=(303.15, 313.15, and 323.15)K and subatmospheric pressure using isochoric saturation method. With the same cation, CO2 solubility in TFA-based BAILs was higher than that in FBA-based ones. From the variation of solubility, expressed as Henry’s law constants, with temperature, the standard Gibbs free energy, enthalpy, and entropy changes of CO2 solvation were calculated. The solubilities of CO2 in these BAILs were apparently increased with increasing the molar volume of BAIL except for [DMFH][TFA].

Bifunctional temperature-sensitive amphiphilic acidic ionic liquids for preparation of biodiesel

Several water-stable bifunctional temperature-sensitive amphiphilic Bronsted-acidic ionic liquids with an alkane sulfonic acid group and a polyether group were synthesized through polyethylene glycol monomethylether as raw material. The properties and structures of the ionic liquids were experimentally characterized. Esterification of oleic acid with methanol to biodiesel was investigated in various bifunctional temperature-sensitive amphiphilic acidic ionic liquids. The amphiphilicity, temperature-sensitive, polymerization degree, acidity and activity correlation for the ionic liquids were studied. It was found that their structures were consistent with the designed structure and their purities were high. Among all these ionic liquids, the ionic liquid – MPEG-350-ILs showed the best catalytic activity that is near to that of concentrated sulfuric acid, which is ascribed to its strong Brønsted acidity and amphiphilicity. The catalytic activity of each ILs is dependent on the polymerization degree of polyether cation. The catalytic activity decreased with lengthening polyether chain of ionic liquids. These ionic liquids exhibited temperature-sensitive property. The produced biodiesel could be separated via simple decantation and the ionic liquids could be reused.

Brønsted acidic ionic liquid catalyzed highly efficient synthesis of chromeno pyrimidinone derivatives and their antimicrobial activity

A series of 8,9-dihydro-2-(2-oxo-2H-chromen-3-yl)-5-aryl-3H-chromeno[2,3-d]pyrimidine-4,6(5H,7H)-diones (5a-j) have been synthesized by the reaction of 2-amino-5,6,7,8-tetrahydro-5-oxo-4-aryl-4H-chromene-3-carbonitrile (4a–j) with coumarin-3-catboxylic acid under neat conditions employing Bronsted acidic ionic liquid (4-sulfobutyl)tris(4-sulfophenyl)phosphonium hydrogen sulfate as catalyst. Structures of all the compounds were established on the basis of analytical and spectroscopic data. All the compounds were evaluated for their in vitro antimicrobial activity against different bacterial and fungal strains.