Imidazolium-based phosphinite ionic liquid (IL-OPPh2) as Pd ligand and solvent for selective dehalogenation or homocoupling of aryl halides

The use of an imidazolium-based phosphinite ionic liquid (IL-OPPh₂) as ligand for Pd offers an efficient reagent system for the selective dehalogenation or homocoupling of aryl halides in the presence of NaOPrⁱ or Et₃N, respectively. This ionic liquid plays a dual role as both the reaction media and also as the potential complexing agent with Pd via its phosphinite carrying group. The ionic liquid containing its corresponding Pd complex can be easily recovered and reused in several runs.     

Physicochemical properties of ionic liquid analogue containing magnesium chloride as temperature and composition dependence

The ionic liquid analogue containing MgCl₂ based on choline chloride and glycerol was reported. The solubility of MgCl₂ in the ionic liquid analogue based on choline chloride and glycerol was measured from T?=?293?C393?K. The empirical equation about the solubility and temperature was obtained. Thermal analysis showed that the ionic liquid analogue was stable from room temperature to 140?°C. The physical properties such as conductivity ??, density ?? and viscosity ?? of ionic liquid analogue were measured as function of the content of MgCl₂ and temperature. An empirical equation about the density (??) and temperature was obtained. The ions transport behaviours are analyzed using hole-theory. It is shown that the conductivity of the ionic liquid analogues is controlled by the ion mobility and the suitable voids.     

Development of sequential type iron salt-catalyzed Nazarov/Michael reaction in an ionic liquid solvent system

Sequential type one pot Nazarov/Michael reaction of pyrrole derivatives has been demonstrated using 5 mol% Fe(ClO4)3·Al2O as catalyst in an ionic liquid as solvent. We succeeded in obtaining 4,5-dihydrocyclopenta[b]pyrrol-6(1H)-one derivative in good yield for five repetitions of the reactions without any addition of the catalyst using an ionic liquid, [bmim][NTf2], as solvent system.     

Fischer—Tropsch synthesis in ionic liquids

A comparative evaluation of the activity of different catalysts in the Fischer—Tropsch synthesis was performed. The reaction was conducted under batch conditions (autoclave) with the catalysts suspended in nonpolar and polar media, viz., n-decane or ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate. The fused Fe—K system, cobalt carbonyl, and pivalate complex [Co(Piv)_2–x OH] _n were used as catalysts. In the most cases, the use of the non-acidic ionic liquid decreases the activity of these catalytic systems. The formation of liquid hydrocarbons С₅—С₁₄ is observed only with the combination ionic liquid—Сo₂(CO)₈. When the Fe—К catalyst is modified with a cocatalyst in the form of the ionic liquid supported on the silica gel surface ([BMIM][BF₄](30%)/SiO₂), the conversion of carbon monoxide somewhat increases (by 5—7%). The ratio paraffins/olefins/iso-paraffins/aromatics in the reaction products was shown to change in a wide range.     

Selective alkylation of phenol with tert-butyl alcohol catalyzed by [bmim]PF6

Alkylation of phenol with tert-butyl alcohol (TBA) in a room temperature ionic liquid, 1-butyl-3-methylimidazoliumhexafluorophosphate ([bmim]PF₆), has been investigated. The effects of various parameters such as reaction temperature, reaction time, reactant ratio (mol ratio of phenol to that of TBA), and the amount of the ionic liquid used were studied. The [bmim]PF₆ ionic liquid was found to catalyze the reaction with high conversion and good selectivity.     

Acidic ionic liquid [NMP]H2PO4 as dual solvent-catalyst for synthesis of β-alkoxyketones by the oxa-Michael addition reactions

Acidic ionic liquid N-methyl-2-pyrrolidonium dihydrogen phosphate [NMP]H₂PO₄ was prepared and used as efficient catalyst and reaction medium to synthesize β-alkoxyketones by the oxa-Michael addition reactions for the first time. The effect of anions and cations, amount of ionic liquid on the reaction was investigated. Various alcohols and phenols proceeded smoothly and led to corresponding β-alkoxyketones with high yields under mild reaction conditions, O-selectivity addition of aminoethanols was also achieved in this paper. Compared with traditional imidazolium ionic liquids, [NMP]H₂PO₄ gave the better results. The ionic liquid was stable and could be reused at least five times with a slight loss of activity.     

Enzyme kinetics assay in ionic liquid-based reaction media by means of Raman spectroscopy and multivariate curve resolution

Enzymatic hydrolysis of p-nitrophenylphosphate by alkaline phosphatase in binary mixtures of water and 1-ethyl-3-methylimidazolium tetrafluoroborate (emimBF₄) was monitored with Raman microspectroscopy. Concentrations of emimBF₄ in the studied ionic liquid/water solvent systems ranged from 0 to 75% v/v. Multivariate curve resolution-alternating least squares (MCR-ALS) was successfully applied to the recorded Raman spectra in order to retrieve the concentration profiles and pure Raman spectra of the different species involved in the reaction. Michaelis-Menten constant (K_M) and maximum rate (V_max) of the reaction were calculated from the initial reaction phase for the different solvent systems studied, to investigate the effect of increasing concentration of the ionic liquid on the kinetic behavior. From this study, it was found that the ionic liquid inhibits the reaction under study decreasing both V_max and K_M.     

Biphasic ethylene polymerisation using 1-n-alkyl-3-methylimidazolium tetrachloroaluminate ionic liquid as a medium of the Cp2TiCl2 titanocene catalyst

A systematic analysis was performed on a series of 1-n-alkyl-3-methylimidazolium tetrachloroaluminates (where alkyl = ethyl, butyl, hexyl, and octyl), applied as a medium of the Cp₂TiCl₂ titanocene catalyst, to evaluate the influence of the physical properties of the ionic liquids on the polymerisation reaction carried out in the biphasic ionic liquid/hexane mode. Two alkylaluminium compounds, AlEtCl₂ and AlEt₂Cl, were used as activators. The influence of the activator/catalyst molar ratio on the performance of the ethylene polymerisation was determined for each ionic liquid studied. The best results were obtained using 1-n-octyl-3-methylimidazolium tetrachloroaluminate. For the titanocene catalyst immobilised in the ionic liquid, AlEtCl₂ turned out to be a better activator than AlEt₂Cl in our studies. The properties of the polyethylene product have also been presented.     

1-Butyl-3-methylimidazolium p-toluenesulfinate: a novel reagent for synthesis of sulfones and β-ketosulfones in ionic liquid

A novel task-specific ionic liquid, 1-butyl-3-methylimidazolium p-toluenesulfinate, [bmim][p-TolSO₂] has been synthesized and used as a nucleophile for the reaction with alkyl bromides and phenacyl bromides to prepare sulfones and β-ketosulfones in excellent yields (80-93%) in [bmim][BF₄] ionic liquid. The isolated yields of sulfones and β-ketosulfones were higher in [bmim][BF₄] than other organic solvents at room temperature.     

Phase behaviour of 1-methyl-3-octylimidazolium bis[trifluoromethylsulfonyl]imide with thiophene and aliphatic hydrocarbons: The influence of n-alkane chain length

This paper reports the results of a new experimental study on the capacity of an ionic liquid to extract a sulfur compound from its mixtures with aliphatic hydrocarbons. With this aim, liquid + liquid equilibrium data of ternary systems containing 1-methyl-3-octyl-imidazolium bis(trifluoromethylsulfonyl)-imide ([C₈mim][NTf₂]), thiophene and n-hexane, n-heptane or n-hexadecane have been determined at T = 298.15 K. All systems showed high solubility of thiophene in the ionic liquid and low solubility of the ionic liquid in the n-alkane. The solute distribution coefficient decreases and the selectivity increases as the chain length of n-alkane increases. Both parameters are higher than unity in most of the cases. The experimental results have been correlated using NRTL activity coefficient model, and large deviations from experimental data have been found at high concentrations of thiophene with the heaviest hydrocarbons.     

[Omim][BF4], a green and recyclable ionic liquid medium for the one-pot chemoselective synthesis of benzoxazinones

An efficient procedure for the one-pot chemoselective synthesis of 2H-benzo[b][1,4]oxazin-3(4H)-one derivatives from their corresponding o-aminophenols is developed using DBU in the ionic liquid [omim][BF₄]. Upon completion of the reaction and separation of the product, the ionic liquid is recovered and successfully reused over nine recycles without any noticeable loss of performance.     

Iron catalyzed Michael addition: Chloroferrate ionic liquids as efficient catalysts under microwave conditions

The iron containing ionic liquid 1-butyl-3-methylimidazolium tetrachloroferrate ([C4mim]Cl/FeCl3; = 0.5) proved to be an efficient catalyst for the solvent-free metal catalyzed Michael addition of β-keto esters and enones. Due to the ionic structure of the catalyst, a significant acceleration of the reaction rate was observed under microwave conditions. Furthermore, recycling of the ionic liquid catalyst could be performed after simply distilling off the products.     

An ionic liquid-mediated expeditious route to the syntheses of diaryl sulfoxides

A fast and efficient protocol is proposed for the synthesis of diaryl sulfoxides in the ionic liquid 1-butyl-3-methylimidazolium chloroaluminate, [bmim]Cl·AlCl₃, N=0.67, by employing arenes and thionyl chloride. The ionic liquid plays a dual role of Lewis acid catalyst and solvent, under ambient conditions, offering good yields of the product. The influence of the Lewis acidity of the ionic liquid on the extent of conversion is studied.     

pTSA-catalyzed one-pot synthesis of 12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthen-11-ones in ionic liquid and neat conditions

Multi-component condensation of β-naphthol, aromatic aldehydes, and cyclic 1,3-dicarbonyl compounds catalyzed by p-toluenesulfonic acid has been accomplished for the synthesis of a series of 12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthen-11-ones in ionic liquid([bmim]BF₄) and in solvent-free media. High yields, ease of recovery, and reusable reaction medium (ionic liquid) with consistent activity makes this protocol efficient and environmentally benign.     

Ionic liquid promoted synthesis of heterocycle-fused pyrimidine-2,4(1H,3H)-diones utilising CO2

An efficient ionic liquid system was developed for the preparation of various heterocycle-fused pyrimidine-2, 4(1H,3H)-diones in moderate to excellent yields (52–95%). It was found that [HDBN⁺][TFE^?], a simple and easily prepared ionic liquid, could act as both the solvent and reaction promoter, and that the reactions could be efficiently carried out at atmospheric pressures of CO₂.     

Volumetric and compressibility behaviour of ionic liquid, 1-n-butyl-3-methylimidazolium hexafluorophosphate and tetrabutylammonium hexafluorophosphate in organic solvents at T = 298.15 K

Density and speed of sound measurements have been made on the systems containing the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) and some organic solvents having a wide range of dielectric constants. Similar studies have been carried out for tetrabutylammonium hexafluorophosphate ([TBA][PF₆]), which has common anion ([PF₆]⁻) with the studied ionic liquid. For the systems investigated, the apparent molar volumes and apparent molar isentropic compressibilities were determined and fitted to the Redlich–Mayer and the Pitzer equations from which the corresponding limiting values were obtained. These limiting values were used to obtain some information about ion–solvent interactions. Furthermore, using the ionic limiting apparent volume values for [TBA]⁺ from the literature and limiting apparent molar volume for the ionic liquid and [TBA][PF₆] obtained in this work, the ionic limiting apparent molar volume values for the cation [BMIM]⁺ in different organic solvents were also estimated.     

Enantioseparation of mandelic acid enantiomers in ionic liquid aqueous two-phase extraction systems

In the past decade, ionic liquids have received great attention owing to their potential as green solvent alternatives to conventional organic solvents. In this work, hydrophobic achiral ionic liquids (1-butyl-3-methylimidazolium-hexafluorophosphate([bmim][PF₆]), 1-octyl-3-methylimidazolium tetrafluoroborate([omim][BF₄])) were used as solvents in chiral liquid-liquid extraction separation of mandelic acid (MA) enantiomers with β-cyclodextrin (β-CD) derivatives as hydrophilic chiral selectors preferentially forming complexes with (R)-enantiomers. Factors affecting the separation efficiency were optimised, namely the type of the extraction solvents and β-CD derivatives, concentrations of the β-CD derivatives and MA enantiomers, pH, and temperature. Excellent enantioseparation of MA enantiomers was achieved in the ionic liquid aqueous two-phase extraction systems under the optimal conditions of pH 2.5 and temperature of 5°C with the maximum enantioselectivity (α) of 1.74. The experimental results demonstrated that the ionic liquid aqueous two-phase extraction systems with a β-CD derivative as the chiral selector have a strong chiral recognition ability, which might extend the application of ionic liquids in chiral separation.     

Osmium catalyzed asymmetric dihydroxylation of methyl trans-cinnamate in ionic liquids, followed by supercritical CO2 product recovery

In this work, osmium-catalyzed asymmetric dihydroxylation (AD) of methyl trans-cinnamate was studied. Osmium and chiral ligand catalysts were immobilized in ionic liquid only, without any other reaction solvents, while the recovery of the product was performed by extraction with supercritical CO₂, and compared with results obtained by extractions with organic solvents such as hexane and diethyl ether. In supercritical CO₂ extraction experiments, optimal extraction pressure was found and ionic liquid chosen, so that the highest reaction yields coupled with lowest osmium content in the crude product can be achieved. Finally, recycle experiments of the same (ionic liquid + catalytic system) mixture were successfully conducted. Application of ionic liquids and supercritical CO₂ in osmium catalyzed AD allows for the isolation of the diol basically without contamination with osmium, in high yield and enantiomeric excess, and it makes possible the efficient reuse of ionic liquid solvent and the catalytic system.     

Direct sulfonylation of Baylis-Hillman alcohols and diarylmethanols with TosMIC in ionic liquid-[Hmim]HSO4: an unexpected reaction

A Brønsted acidic ionic liquid-[Hmim]HSO₄ promoted unexpected reaction of Baylis-Hillman alcohols and diarylmethanols with p-toluenesulfonylmethyl isocyanide (TosMIC) affording the corresponding sulfone derivatives instead of N-tosylmethyl amides is reported. After isolation of the product, the ionic liquid [Hmim]HSO₄ was easily recycled for further use.     

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.