Direct ionic liquid promoted organocatalyzed diazo-transfer reactions: diversity-oriented synthesis of diazo-compounds

A practical and novel ionic liquid promoted organocatalytic selective diazo-transfer process for the synthesis of highly substituted diazo-compounds in high yields is reported. The ionic liquid can be reused without affecting the reaction rates or yields over five runs.     

Viscosity of (C2-C14) 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ionic liquids in an extended temperature range

Dynamic viscosities of several members of the 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, [C_nmim][NTf₂], ionic liquids family, with the cation alkyl side-chain length varying from 2 to 14 carbon atoms, have been measured in the 278.15 K to 393.15 K temperature range using two different apparatuses. To the best of our knowledge, it is the first time that such an extensive assessment of viscosity - in terms of the number of compounds of a single ionic liquid homologous series, of the broad range of temperature covered, and the use of two different experimental techniques - is reported. The use of two different instruments, using different methodologies, provides information about the uncertainties in the measurement of viscosity of ionic liquids, including its dependence on the presence of traces of water and other impurities. An extensive critical analysis of the deviations between the data measured in this work and those reported in literature has been carried out.     

Design and synthesis of novel ionic liquid/liquid crystals (ILCs) with axial chirality

As the first examples of axially chiral ionic liquids, new pyridinium salts having a 1,3-dioxan ring in their central core were synthesized. Enantioselective dehydrohalogenation using chiral alkoxides provided a simple and practical approach for their synthesis. Some structures exhibit both low melting point and liquid crystalline behaviour.     

Solvent-free aza-Markovnikov and aza-Michael additions promoted by a catalytic amount of imidazolide basic ionic liquids

A family of imidazolide ionic liquids were synthesized and characterized. These ionic liquids combined the virtues of strong basicity and relatively good thermal stability. Catalytic properties of these imidazolide ionic liquids were investigated and satisfactory yield was achieved when 2.0 mol % of [Bmim]Im was used as catalyst for aza-Markovnikov addition under solvent-free condition at room temperature in one hour. Experimental results show that a hydrogen bond is not formed between [Bmim]Im/imidazole and vinyl ester, and its existence is not necessary for the [Bmim]Im catalyzed aza-Markovnikov addition either. A possible mechanism for [Bmim]Im-catalyzed aza-Markovnikov addition was proposed. The use of imidazolide ionic liquids in aza-Michael addition was investigated as well.     

Asymmetric Michael addition promoted by (R,R)-trans-1,2-diaminocyclohexane in ionic liquids

In tetrafluoroborate based ionic liquids fair yields and enantiomeric excesses up to 91% were obtained in the Michael addition of ethyl cyclohexanone-2-carboxylate to methyl vinyl ketone, using (R,R)-trans-1,2-diaminocyclohexane as chiral auxiliary (37% mol/mol with respect to the donor). The presence of catalytic amounts of metal sources [Ni(OAc)₂ · 4H₂O, Co(acac)₂, FeCl₃ · 6H₂O, LaCl₃, Cu(OAc)₂ · H₂O] did not improve the activity, and, in some instances, caused a drop of enantioselectivity. Reactions carried out in the absence of any metal and with a Michael donor/diamine molar ratio of 20 allowed us to ascertain that the reaction can be performed catalytically.     

Chlorozincate(II) acidic ionic liquid: Efficient and biodegradable silylation catalyst

A practical and highly efficient silylation of alcohol and phenol derivatives with hexamethyldisilazane (HMDS) using acidic ionic liquids under mild reaction conditions is described. A series of Brønsted as well as Brønsted–Lewis acidic ionic liquids were prepared and their performance investigated for the silylation of a wide variety of alcohols and phenols with HMDS. Imidazole‐ as well as N ‐methyl‐2‐pyrrolidone‐based acidic ionic liquids have a higher catalytic activity for the protection of sensitive, hindered alcohols and phenols, thus providing an environmentally begin and versatile alternative to current acid catalysts. In addition, the acidic ionic liquids are reusable, being recovered easily and reused several times without significant deterioration in catalytic activity.     

Analysis by desorption of volatile impurities from an ionic liquid solution in an unmodified gas chromatograph inlet

A procedure for using ionic liquids to determine volatile impurities in compounds or matrices that are soluble in an ionic liquid is described. Using a conventional autosampler a droplet of ionic liquid solution is suspended in the inlet of the gas chromatograph and analytes are desorbed onto a GC column using splitless injection conditions. Results are presented for 1,2-propanediol, nonane, N,N-dimethylacetamide, and mesitylene in two different compounds in the ionic liquids trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide and trihexyltetradecylphosphonium dicyanamide.     

A facile and economical procedure for the synthesis of maleimide derivatives using an acidic ionic liquid as a catalyst

Seven maleimide derivatives were synthesized in good yields and high purity from the corresponding maleamic acids using a Brønsted acidic room temperature ionic liquid (RTIL) as a catalyst. The products were obtained through merely a decanting and removal of the solvent, suggesting that this procedure is superior to the conventional routes, in which the strong organic/inorganic acids were used as the catalysts, as well as a complicated post-processing procedure for the separation and purification of the products was employed.     

Efficient synthesis of chlorohydrins: ionic liquid promoted ring-opening reaction of epoxides and TMSCl

The environmentally benign, highly efficient synthesis of chlorohydrins by cleavage of epoxides using TMSCl in ionic liquid, bmimPF₆, has been studied.     

Use of selective ionic liquids and ionic liquid/salt mixtures as entrainer in a (vapor + liquid) system to separate n-heptane from toluene

During the last years, a large number of studies have evaluated the ability of ionic liquids (ILs) to separate aromatic from aliphatic hydrocarbons by liquid extraction. Nevertheless, in order to design a global process, a post-extraction step based on the aromatic recovery from the extract stream and the regeneration of the IL is required. Taking into account the negligible vapor pressure of the ILs, the use of separation units based on the difference of volatility among the components of the extract could be an appropriate way. However, that requires additional (vapor + liquid) equilibrium (VLE) data, which are scarce today. In this work, the isothermal VLE data for {n-heptane + toluene + 1-ethyl-3-methylimidazolium thiocyanate ([EMim][SCN])} and {n-heptane + toluene + 1-butyl-3-methylimidazolium thiocyanate ([BMim][SCN])} mixtures were experimentally measured at T = (323.2, 343.2 and 363.2) K over the whole composition range within the rich-IL miscibility region. For that, a static headspace gas chromatograph (HS-GC) was used. In addition, the non-random two liquids (NRTL) thermodynamic model was satisfactory applied to correlate the experimental VLE data.Finally, the effect of thiocyanate-based inorganic salts (AgSCN, Co(SCN)₂ and CuSCN) on the phase behavior of the above mentioned mixtures were also analyzed through the experimental determination of the isothermal VLE of the pseudo-ternary systems {n-heptane + toluene + [EMim][SCN]/salt mixture}.The obtained results show that the use of pure thiocyanate-based ILs as entrainer increases the n-heptane relative volatility from toluene whereas the addition of inorganic salts has not led to an improvement of these results.     

Isomerization of cyclic hydrocarbons mediated by an AlCl3-based ionic liquid as catalyst

Cyclohexane and methylcyclopentane isomerization were carried out under mild conditions using an ionic liquid consisting of n-butylpyridinium chloride and aluminum chloride as catalyst. The ionic liquid showed reasonably high catalytic activity in both reactions with a selectivity to corresponding products of 100%. In the case of cyclohexane isomerization, the thermodynamic equilibrium methylcyclopentane ⇌cyclohexane was almost achieved. For the reaction of cyclohexane isomerization, the kinetic study was performed, and the rate constants and the activation energy of the process were determined. This revised version was published online in June 2006 with corrections to the Cover Date.     

Stereoselective syntheses of unnatural steroidal C(20R) aldehydes by ionic hydrogenation of C-20 tertiary alcohols

Syntheses of three unnatural steroidal C(20R) aldehydes have been realised from 16-dehydropregnenolone acetate. The salient feature of the synthesis is the ionic hydrogenation of C-20 tertiary alcohols leading to the formation of the C(20R) unnatural isomer with complete stereoselectivity. Oxidative hydrolysis of the dithiane moiety furnished the C(20R) aldehydes.     

Estimation of physico-chemical properties of ionic liquid [C7mim][BF4]

Ionic liquid (IL) [C₇mim][BF₄] (1-heptyl-3-methyl-imidazolium tetrafluoroborate) was prepared and characterized. The density and surface tension of the IL were determined in the temperature range of 293.15–343.15 K. In terms of Glasser's theory, the standard molar entropy and lattice energy of the IL were estimated. Using Kabo's method, the molar enthalpy of vaporization of the IL, Δ_l^gH_m⁰ (298 K), was estimated. According to the interstice model, the thermal expansion coefficient of IL, α, was calculated and in comparison with experimental value, they are within one order of magnitude.     

Improved activity of horseradish peroxidase (HRP) in ‘specifically designed’ ionic liquid

The ionic liquid (IL), tetrakis (2-hydroxyethyl) ammonium triflouromethanesulfonate is rationally designed for horseradish peroxidase (HRP) on the basis of its stability and activity in the presence of an excipient, tris(hydroxymethyl)aminoethane (TRIS) in different ILs. The activity of HRP in this tailor made IL is at least 30-240-fold higher than that in conventional ILs. Also, the activity is more than 10 times greater than that in methanol, a common organic solvent used for HRP.     

(Liquid + liquid) equilibria for mixtures of dodecane and ethanol with alkylsulfate-based ionic liquids

The ternary (liquid + liquid) equilibrium (LLE) data for mixtures of dodecane (C₁₂H₂₆) and ethanol with ionic liquids 1,3-dimethylimidazolium methylsulfate [Mmim][MeSO₄], 1-ethyl-3-methylimidazolium methylsulfate, [Emim][MeSO₄] and 1-butyl-3-methylimidazolium methylsulfate, [Bmim][MeSO₄], were studied at T = 298.15 K and 0.101 MPa. The selectivity and solute distribution coefficient ratios determined from the data were used to examine the possibility of using these ionic liquids for extraction of ethanol from dodecane. The temperature dependency was investigated by measuring the LLE data for {dodecane + ethanol + [Mmim][MeSO₄]} at T = 313.15 K and 0.101 MPa. The Othmer–Tobias and Hand equations were used to test the consistency of the tie-line data. The tie-line data were correlated with the Non-Random Two Liquid (NRTL) equation which provided a good model and representation for the experimental results.     

The importance of complex stability for asymmetric copper-catalyzed cyclopropanations in [emim][OTf] ionic liquid: the bis(oxazoline)-azabis(oxazoline) case

Azabis(oxazoline)-Cu complexes are more stable than their analogues based on bis(oxazoline) ligands. This increased stability leads to improved recoverability (up to eight times) when these systems are used in an ionic liquid medium. The solution of the chiral catalyst can even be reused in different enantioselective cyclopropanation reactions and still lead to high enantiomeric excess (>90%).     

Synthesis of batracylin and its N-sulfonamido analogues in [b-3C-im][NTf2] ionic liquid

Starting with commercial and inexpensive reagents, a high-yielding chemical process carried out in [b-3C-im][NTf₂] ionic liquid was achieved to afford the synthesis of batracylin and its N-sulfonamido analogues. Among all compounds synthesized, compounds 1, 11, and 14 exhibit potent inhibitory activity against human topoisomerase 1 (hTop1).     

Ionic liquid promoted palladium-catalyzed Suzuki cross-couplings of N-contained heterocyclic chlorides with naphthaleneboronic acids

Suzuki cross-couplings of N-contained heterocyclic chlorides with naphthaleneboronic acids in the ionic liquids can be performed with excellent yield. The use of ILs appears to be advantageous in comparison with the conventional organic solvent; products with good purity and higher yield were obtained with shorter reaction time, the product isolation was simple and the ILs could be reused.     

Nuclear magnetic resonance spectroscopic studies of the trihexyl (tetradecyl) phosphonium chloride ionic liquid mixtures with water

Tetra-alkyl Phosphonium ionic liquids are phosphonium salts with melting points near room temperature. We report the NMR studies of water-trihexyl (tetradecyl) phosphonium chloride ionic liquid mixtures. The proton chemical shifts were used to investigate the intermolecular interactions in mixtures of ionic liquids and water. The OH chemical shifts were found to decrease as the water concentration in the ionic liquid increased, and their rate of change with temperature decreased with water concentration. The CH₂ and CH₃ chemical shifts were found to move downfield with the increase in temperature, and moved further downfield as water concentration was decreased. The interface of experimental data and the results of quantum calculations suggest a significant binding of phosphonium cations to chloride anion and water molecules. As well, the analysis of the data suggests a possible transformation from cationchloride-water configuration at low water concentrations to cation-water-water at higher water concentrations. Electronic Supplementary Material  Supplementary material is available for this article at and is accessible for authorized users.     

A new synthesis of acetamido phenols promoted by Ce(SO4)2

A new method for the synthesis of acetamido phenols by a one-pot, three-component Ritter type reaction in moderate to good yields is described. Both electron donating and electron releasing substitution on aromatic rings are tolerated.