1- -3-methylimidazolium tetrafluoroborate

Lipases from C. antarctica and P. cepacia showed higher enantioselectivity in the two ionic liquids l-ethyl-3-methylimidazolium tetrafluoroborate and l-butyl-3-methylimidazolium hexafluoroborate than in THE and toluene, in the kinetic resolution of several secondary alcohols [49]. Similarly, with lipases from Pseudomonas species and Alcaligenes species, increased enantioselectivity was observed in the resolution of 1 -phenylethanol in several ionic liquids as compared to methyl tert-butyl ether [50]. Another study has demonstrated that lipase from Candida rugosa is at least 100% more selective in l-butyl-3-methylimidazolium hexafluoroborate and l-octyl-3-nonylimidazolium hexafluorophosphate than in n-hexane, in the resolution of racemic 2-chloro-propanoic acid [51]. 

As reported by Griengl and coworkers, benzaldehyde, decanal, undecanal, and dodecanal were reacted with HCN in a two-phase solvent system aqueous buffer and ionic liquids 1 -ethyl-3-methylimidazolium tetrafluoroborate, 1 -methyl-3-propylimidazolium tetrafluoroborate, and l-butyl-3-methyl-imidazolium tetrafluoroborate in the presence of the HNLs from Prunus amygdalus and Hevea brasiliensis. When compared with the use of organic solvents as the nonaqueous phase, the reaction rate was significantly increased and the enantioselectivity remained good [51]. 

Alkylation at nitrogen has been achieved by treating indole or pyrrole with alkyl halides in ionic solutions of potassium carbonate in l- -butyl-3-methylimidazolium tetrafluoroborate [bmim][BFJ <06TL2435>. Bis-protection of 3,3 -diiodo-2,2 -biindoles with Me, Boc, C02Et, or S02Ph has been described by Roy and Gribble <06SC3487>. 

A basic ionic liquid, l-methyl-3-butylimidazolium hydroxide ([bmIm]OH) and l-butyl-3-methyl-methylimidazolium tetrafluoroborate ([bmim]BF4), has been introduced as a catalyst and reaction medium for the Markovnikov addition of imidazoles 116 to vinyl esters 115 under mild conditions to give imidazoesters 117 <06JOC3991 06TL1555>. A series of (nitroimidazolyl)succinic esters and diacids were prepared from the Michael-type addition of the nitroimidazole to the a,P-unsaturated ester <06S3859>. 

One of the important new directions in the study of addition reactions of organozinc compounds to aldehydes is the use of ionic liquids. Usually, application of these compounds in reactions with common organometallic reagents has a serious problem ionic solvents are usually reactive toward them, particularly Grignard and organolithium derivatives. It has been recently reported that carbonyl compounds react with allylzinc bromide formed in situ from allyl bromide and zinc in the ionic liquid 3-butyl-l-methylimidazolium tetrafluoroborate, [bmim][BF4].285 Another important finding is that the more reactive ZnEt2 alkylates aldehydes in a number of ionic liquids at room temperature.286 The best yields (up to 96%) were obtained in A-butylpyridinium tetrafluoroborate, [bpy][BF4] (Scheme 107). 

Recently, there has been considerable interest in developing molten salts that are less air and moisture sensitive. Melts such as l-methyl-3-butylimidazolium hexa-fluorophosphate [211], l-ethyl-3-methylimidazolium trifluoromethanesulfonate [212], and l-ethyl-3-methylimidazolium tetrafluoroborate [213] are reported to be hydro-phobic and stable under environmental conditions. In some cases, metal deposition from these electrolytes has been explored [214]. They possess a wide potential window and sufficient ionic conductivity to be considered for many electrochemical applications. Of course if one wishes to take advantage of their potential air stability, one loses the opportunity to work with the alkali and reactive metals. Further, since these ionic liquids are neutral and lack the adjustable Lewis acidity common to the chloroaluminates, the solubility of transition metal salts into these electrolytes may be limited. On a positive note, these electrolytes are significantly different from the chloroaluminates in that the supporting electrolyte is not intended to be electroactive. 

Holbrey, J. D. Seddon, K. R. The phase behaviour of l-alkyl-3-methylimidazolium tetrafluoroborates ionic liquids and ionic liquid crystals, J. Chem. Soc., Dalton Trans., 1999, 2133-2139. 

The typical in situ reduction of the precursor [lr(COD)Cl]2 by molecular hydrogen under the same reaction conditions have been also performed in 1-n-butyl-3-methylimidazolium trifluoromethanesulfonate (BMl-CFsSOs) and 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMl-BF [25]. The iridium nanoparticles prepared in BMTCF3SO3 and BM1-BF4 ILs, as previously observed with BM1-PF6, display irregular shapes with a monomodal size distribution (Figure 15.4). Mean diameters in the range of 2-3 nm were estimated with in situ TEM and small-angle X-ray scattering (SAXS) analyses of the lr(0) nanoparticles soluble in the ionic hquids, and by X-ray diffraction (XRD) of the isolated material. The mean diameters of iridium nanoparticles synthesized in the three ILs, as estimated by TEM, SAXS and XRD, are summarized in Table 15.1. 

In the process of developing the Stetter reaction in ionic liquids, Gree and coworkers applied their methodology to the synthesis of haloperidol (Scheme 25) [101], A variety of aromatic aldehydes react with methyl acrylate 160 when butyl-methylimidazolium tetrafluoroborate [bmim][BF ] is used as solvent. In the synthesis of haloperidol, electron-deficient aldehyde 153 was subjected to standard reaction conditions with 160 to provide 161 in good yield. 

Putilova ES, Troitskii NA, Zlotin SG, Khudina OG, Burgart YV, Saloutin VI, Chupakhin ON (2006) One-step solvent-free synthesis of fluoroalkyl-substituted 4-hydroxy-2-oxo(thioxo) hexahydropyrimidines in the presence of l-butyl-3-methylimidazolium tetrafluoroborate. Russ J Org Chem 42 1392-1395... 

Butyl-3-methylimidazolium tetrafluoroborate IH-lmidazolium, 1-butyl-3-methyl-, tetrafluoroborate(l-) (13) (174501-65-6)... 

Three ionic liquids were purchased from Aldrich l-butyl-3-methylimidazolium chloride, l-butyl-3-methylimidazolium hexafluorophosphate and l-butyl-3-methylimidazolium tetrafluoroborate. Homogeneous Co (II) catalyst precursors used in our experiments include Co(BF4)2, Co(OAc)2, and Co(C104)2 each of which have high solubilities in above ionic liquids. High surface area catalyst supports Si02 and AI2O3 were obtained from Davison and Engelhard, respectively. 

Figure 3.1-4 Changes in liquefaction points for 1 -alkyl-3-methylimidazolium tetrafluoroborate and bis(trifyl)imide ionic liquids as a function of chain length, showing true melting points (solid fill) and glass transitions (open symbols).

The double carbonylation of iodobenzene with diethylamine catalyzed by Pd(OAc)2-PPh3 was carried out in l-butyl-3-methylimidazolium tetrafluoroborate 315 as reaction medium at 80 °C and 38 atm of CO to give phenyl-glyoxamide 314 as the predominant product (83%) accompanied by benzamide 313 (17%) (Equation (29)). The use of ionic liquids showed the same reactivity and product selectivity as those using diethylamine as solvent for this reaction, while separation of products and recycling of the catalyst was easier. ... 

The synthesis of a-methylene-7-lactone 317 through carbonylation of but-3-yn-l-ol 316 catalyzed by Pd(ll)-PPh2(2-Py) has been carried out in l-butyl-3-methylimidazolium tetrafluoroborate 315 as reaction medium in high yield with excellent product selectivity (Equation (30))4 Although the ionic liquid containing the catalytic species was recovered, a significant decrease in yield occurred with the recycled catalyst, which appears to be attributed to the decomposition of the catalyst during the isolation procedure ... 

Nishida, T., Tashiro, Y., and Yamamoto, M., Physical and electrochemical properties of l-alkyl-3-methylimidazolium tetrafluoroborate for electrolyte. Fluorine Chem., 120,135,2003. 

Gomes de Azevedo, R. et al.. Thermophysical and thermodynamic properties of l-butyl-3-methylimidazolium tetrafluoroborate and l-butyl-3-methylimid-azolium hexafluorophosphate over an extended pressure range, ]. Chem. Eng. Data, 50, 997, 2005. 

Letcher, T.M. and Reddy, R, Ternary liquid-liquid equilibria for mixtures of l-hexyl-3-methylimidazolium (tetrafluoroborate or hexafluoroborate) + benzene + an alkane at T = 298.2 K and 1 atm, /. Chem. Thermodyn., 37, 415,2005. 

Letcher, T.M. et al.. Determination of activity coefficients at infinite dilution of solutes in the ionic liquid l-hexyl-3-methylimidazolium tetrafluoroborate using gas-liquid chromatography at the temperatures 298.15 K and 323.15 K, /. Chem. Eng. Data, 48, 1587, 2003. 

Mutelet, F. and Jaubert, J-N., Measurements of activity coefficients at infinite dilution in l-hexadecyl-3-methylimidazolium tetrafluoroborate ionic liquid, /. Chem Thermodyn., 39,1144,2007. 

Ding, S.F., Xu, M.Q., Zhao, G.C., and Wei, X.W., Direct electrochemical response of Myoglobin using a room temperature ionic liquid, l-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate, as supporting electrolyte, Electrochem. Commun., 9, 216-220,2007. 

Wang, S.F., Chen, T., Zhang, Z.L., Pang, D.W., and Wong, K.Y., Effects of hydrophobic room-temperature ionic liquid l-butyl-3-methylimidazolium tetrafluoroborate on direct electrochemistry and biocatalysis of heme proteins entrapped in agarose hydrogel films, Electrochem. Commun., 9, 1709-1714, 2007. 

The imidazolium ions present in the CE BGE coat the capillary walls, generating an anodic EOF at low pH values (see Figure 6.5). The direction and magnitude of EOF essentially depend on pH of BGE. The change of direction of EOF fakes place befween pH 7.5 and 8 in fhe case of l-ethyl-3-methylimidazolium tetrafluoroborate ([C2Cjlm][BFJ) [44]. 

Jacquemin, J. et al.. Solubility of carbon dioxide, ethane, methane, oxygen, nitrogen, hydrogen, argon, and carbon monoxide in l-butyl-3-methylimidazolium tetrafluoroborate between temperatures 283 K and 343 K and at pressures close to atmospheric, /. Chem. Thermodyn., 38, 490, 2006. 

The ILs interact with surfaces and electrodes [23-25], and many more studies have been done that what we can cite. As one example, in situ Fourier-transform infrared reflection absorption spectroscopy (FT-IRAS) has been utilized to study the molecular structure of the electrified interphase between a l-ethyl-3-methylimidazolium tetrafluoroborate [C2Qlm][BF4] liquid and gold substrates [26]. Similar results have been obtained by surface-enhanced Raman scattering (SERS) for [C4Cilm][PFg] adsorbed on silver [24,27] and quartz [28]. 

Figure 12.17 Raman spectra of l-alkyl-3-methylimidazolium tetrafluoroborate liquids, [C CiIm][Bp4] for n = 10, 8, 7, 6, 5, 4, 3, and 2. (Adapted from Hamaguchi, H., and Ozawa, R., Adv. Chem. Phys., 131,85-104, 2005. With permission.)...

The Diels-Alder reaction is an important and widely used reaction in organic synthesis (Sauer and Sustmann, 1980), and in the chemical industry (Griffiths and Previdoli, 1993). Rate enhancement of this reaction has been achieved by the use of solvents such as water, surfactants, very high pressure, lithium amides, alkylammonium nitrate salts, and macrocyclic hosts (Sherman et ak, 1998). Diels-Alder reactions can be ran in neutral ionic liquids (such as 1-butyl-3-methylimidazolium trifluoromethanesulfo-nate, l-butyl-3-methylimidazolium hexafluorophophate, l-butyl-3-methylimidazolium tetrafluoroborate, and l-butyl-3-methylimidazolium lactate). Rate enhancements and selectivities are similar to those of reactions performed in lithium perchlorate-diethyl ether mixtures. 

The Stille coupling reaction has been performed in l-bntyl-3-methylimidazolium tetrafluoroborate. Use of this solvent system allows for facile recycling of the solvent and catalyst system, which can be used at least five times with little loss in activity. An interesting preference in starting catalyst oxidation state for nse with aryl bromides and aryl iodides was observed (Handy and Zhang, 2001). 

Palladium-catalyzed arylation of the electron-rich olefin bntyl vinyl ether has been accomplished in the ionic liquid l-butyl-3-methylimidazolium tetrafluoroborate using as the arylating agents aryl iodides and bromides instead of the commonly used, but commercially unavailable and expensive, aryl triflates. The reaction proceeds with high efficiency and remarkable regioselectivity, leading almost exclnsively to substitution by various aryl groups at the olefinic carbon a to the heteroatom of butyl vinyl ether (Xu et ak, 2001). 

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