Heteropolyanion-based Ionic Liquids Research Articles

An eco-benign and highly efficient procedure for N-acylation catalyzed by heteropolyanion-based ionic liquids using carboxylic acid under solvent-free conditions

An eco-benign and highly efficient route for N-acylation of amines has been developed by treating amines with corresponding carboxylic acids in the presence of 2 mol % of heteropolyanion-based ionic liquids as catalysts under solvent-free conditions. This practical reaction could tolerate a wide range of substrates. Thus, various N-acylation products including N-acyl α-amino acid derivatives were obtained in moderate to excellent yields at 70 °C to 120 °C. Moreover, recycling studies revealed that heteropolyanion-based ionic liquids were easily reusable for this N-acylation. This method provides a green and much improved protocol over the existing methods.

Synthesis of immobilized heteropolyanion-based ionic liquids on mesoporous silica SBA-15 as a heterogeneous catalyst for alkylation

Phosphotungstic acid (H3PW12O40) has been successfully loaded onto sulfonate-functionalized ionic liquid-modified mesoporous silica SBA-15 by complete anion exchange. The obtained catalysts were highly effective for alkylation of o-xylene with styrene in terms of yield and stability.

A Green and Efficient Protocol for the Synthesis of Quinoxaline, Benzoxazole and Benzimidazole Derivatives Using Heteropolyanion-Based Ionic Liquids: As a Recyclable Solid Catalyst

In this paper, we introduce two nonconventional ionic liquid compounds which are composed of propane sulfonate functionalized organic cations and heteropolyanions as green solid acid catalysts for the highly efficient and green synthesis of 2,3-disubstitutedquinoxaline derivatives. These ionic liquids are in the solid state at room temperature and the synthesis is carried out via the one-pot condensation reaction of various o-phenylenediamine with 1,2-diketone derivatives. Benzoxazole and benzimidazole derivatives were also synthesized by these novel catalysts via the one-pot condensation from reaction orthoester with o-aminophenol (synthesis of benzoxazole derivatives) and ophenylenediamine (synthesis of benzimidazole derivatives). All experiments successfully resulted in the desired products. The described novel synthesis method has several advantages of safety, mild condition, high yields, short reaction times, simplicity and easy workup compared to the traditional method of synthesis.

Synthesis of amidoalkyl naphthol via Ritter-type reaction catalysed by heteropolyanion-based ionic liquid

A facile and efficient procedure for the preparation of amidoalkyl naphthols via a Ritter-type reaction of 2-naphthol, aromatic aldehydes and amide in the presence of heteropolyanion-based functionalized ionic liquid has been described. The one-pot solvent-free three-component reaction is accomplished at 110°C for 5–10 min in reasonable to good yield ranging from 73% to 94%. The catalyst could be recovered and reused at least six times without noticeably decreasing the catalytic activity. Heteropolyanions-based functionalized ionic liquid catalysed the synthesis of amidoalkyl naphthols via one-pot three-component Ritter-type reaction under solvent-free conditions. The reaction was accomplished at 110°C for 5–10 min to afford reasonable to good yields ranging from 73% to 94%.

Deep Desulfurization of Fuels by Heteropolyanion-Based Ionic Liquid

A new heteropolyanion-based ionic (<TEX>$[Hmim]_5PMo_{10}V_2O_{40}$</TEX>) was synthesized by the reaction of molybdovanadophosphoric acid (<TEX>$H_5PMo_{10}O_{40}$</TEX>) with N-methylimidazole. [<TEX>$[Hmim]_5PMo_{10}V_2O_{40}$</TEX> showed a high catalytic activity in the oxidative desulfurization of sulfur-containing compounds in 1-methylimidazolium tetrafluoroborate (<TEX>$[Hmim]BF_4$</TEX>) ionic liquid using 30% aqueous <TEX>$H_2O_2$</TEX> as the oxidant. The catalytic system was of high activity, simplified workup and flexible recyclability. The catalytic oxidation reactivity of sulfur-containing compounds decreased in the order dibenzothiophene (DBT) > 4,6-dimethyldibenzothiophene (4,6-DMDBT) > benzothiophene (BT). The influences of various parameters including reaction time (t) and temperature (T), catalyst dosage, and oxidant to sulfur molar ratio n(O)/n(S) on the desulfurization of model oil were investigated in details. 99.1% of DBT conversion in the model oil was achieved at atmospheric pressure under the optimal conditions: n(O)/n(S) = 4:1, <TEX>$60^{\circ}C$</TEX>, 100 min and molar ratio of catalyst to sulfur of 0.062. The ionic liquid can be recycled six times without significant decrease in activity.

Heterogeneous Beckmann Rearrangements Catalyzed by a Sulfonated Imidazolium Salt of Phosphotungstate

The heteropolyanion-based ionic liquid (IL) material [MIMPS]3PW12O40, propane sulfoacid-functionalized imidazolium salt of phosphotungstate, was used as a solid catalyst for liquid-phase Beckmann rearrangements of ketoximes in the presence of zinc chloride. The resultant liquid–solid biphasic rearrangement reaction of cyclohexanone oxime shows a high yield 83 % with good recyclability. The testing of control catalysts, reaction conditions, oxime substrates, and recycling property were carried out and the results are discussed. The heteropolyanion-based ionic liquid (IL) material [MIMPS]3PW12O40, propane sulfoacid-functionalized imidazolium salt of phosphotungstate, was used as a solid catalyst for liquid-phase Beckmann rearrangements of ketoximes in the presence of zinc chloride. The resultant liquid-solid biphasic rearrangement reaction of cyclohexanone oxime shows a high yield 83% with good recyclability. The testing of control catalysts, reaction conditions, oxime substrates, and recycling property were carried out, and the results are discussed.

Heteropolyanion-Based Ionic Liquid for Deep Desulfurization of Fuels in Ionic Liquids

A heteropolyanion-based ionic liquid, [(3-sulfonic acid) propylpyridine]3PW12O40·2H2O, [PSPy]3PW12O40·2H2O, abbreviated [PSPy]3PW, was synthesized and approved as an effective catalyst for desulfurization of fuels in [omim]PF6 by using aqueous H2O2 as oxidant. The catalysis was fulfilled with advantages of high activity, simplified workup, and flexible recyclability. The catalytic oxidation reactivity of sulfur-containing compounds was in the order dibenzothiophene (DBT) > 4,6-dimethyldibenzothiophene (4,6-DMDBT) > benzothiophene (BT). The effects of the amount of [PSPy]3PW, H2O2, and reaction time and temperature were investigated in detail. Under the optimal conditions, the removal of DBT achieved 99.4%. Especially, we found that the removal of 4,6-DMDBT could be up to 98.8%, and the system could be recycled at least 9 times without significant decrease in activity. The sulfur level of FCC gasoline could be reduced from 360 to 70 ppm in the extraction and catalytic oxidation system.