L-butyl-3-methylimidazolium-tetrafluoroborate

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>. 

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... 

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. 

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 ... 

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. 

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. 

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 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. 

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). 

Li N, Zhang S, Li X et al (2009) Effect of polyethylene glycol (PEG-400) on the l-butyl-3-methylimidazolium tetrafluoroborate-in-cyclohexane ionic liquid microemulsion. Colloid Polym Sci 287(1) 103-108... 

Palladium-catalyzed Suzuki cross-coupling reactions can be conducted in the ambient temperature ionic liquid, l-butyl-3-methylimidazolium tetrafluoroborate (29), in which unprecedented reactivities are witnessed, and which allows easy product isolation and catalyst recycling (Eq. (60)) [96]. 

Liu Y, Wang M, Li J et al (2005) Highly active horseradish peroxidase immobilized in l-butyl-3-methylimidazolium tetrafluoroborate room-temperature ionic liquid based sol-gel host materials. Chem Commun 1778-1780... 

A similar principle is applied in dispersion polymerization in ionic liquids produced particles are in sub-micron range (41,42). The monomer, initiator and colloidal stabilizer are soluble in the liquid medium, but the obtained polymer is not. Different kinds of ionic liquids may be used, such as for styrene l-butyl-3-methylimidazolium tetrafluoroborate or N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide. In general, radical polymerization in ionic liquids provides higher polymerization rate and higher molecular weights than the process in bulk or organic solvents (homogenous system). 

The major impurities contained in RTILs are water and oxygen, even in highly pure samples. This is because these molecules are easily dissolved into the RTILs from air. Since these molecules are electrochemicaUy active, the removal of these molecules is essential before any voltammetric measurement. The effect of water on the EW of RTILs has been studied in RTILs containing the imidazoHum cation and fluoroanions (l-butyl-3-methylimidazolium tetrafluoroborate or hexafluoro-phosphate). Both the Ecl and Eal are reported to have shifted toward positive and negative potentials, respectively, with the addition of more than 3 wt% of water,... 

In bmim BF4, l-butyl-3-methylimidazolium tetrafluoroborate Dyson, P.J. Ellis, D.J. Parker, D.G. Welton, T. Chem. Commun. 1999, 25. 

In bmim BF4 and CIO4 l-butyl-3-methylimidazolium tetrafluoroborate and perchlorate Fischer, T. Sethi, A. Welton, T. Woolf, J. Tetrahedron Lett. 1999, 40, 793. In chloroaluminates Lee, C.W. Tetrahedron Lett 1999, 40, 2461. In phosphonium tosylates Ludley, P Karodia, N. Tetrahedron Lett. 2001, 42, 2011. In pyridinium salts Xiao, Y MaUiotra, S.V. Tetrahedron Lett. 2004, 45, 8339. In HBuIm, hydrogenbutylimidazolium tetrafluoroborate and DiBuIm, 1,3-dibutylimidazolium, tetrafluoroborate Jaegar, D. A. Tucker, C. E. Tetrahedron Lett. 1989, 30, 1785. 

For oxidation with KMn04 on alumina with no solvent, see Hajipour, A.R. Mallakpour, S.E. Imanzadeh, G. Chem. Lett. 1999, 99. For oxidation with silica-supported KMn04, see Takemoto, T. Yasuda, K. Ley, S.V. Synlett 2001, 1555. For oxidation in the ionic liquid bmim BF4, l-butyl-3-methylimidazolium tetrafluoroborate Kumar, A. Jain, N. Chauhan, S.M.S. Synth, Commun. 2004, 34, 2835. 

Dialkylimidazolium ionic liquids with BF4 and IT), anions are quite stable and while being polar (see below) are also non-nucleophilic. They can be prepared in a variety of ways, most commonly by metathesis reactions21-23 and also by a methylation reaction.24 These reactions are illustrated in Schemes 2 and 3, respectively. The chloride produced in the metathesis reactions (Scheme 2) is very difficult to remove completely and it effects the physical properties of the liquid and can also effect certain reactions carried out in the liquid. Figure 6 shows how the viscosity of l-butyl-3-methylimidazolium tetrafluoroborate varies with chloride concentration.25... 

Many of the methods that were previously employed for Mn(OAc)3-medi-ated radical reactions involved the use of acetic acid as a solvent. Because of the poor solubility of Mn(OAc)3 in organic solvents and the need for high temperatures for many reactions, the use of acetic acid limited the range of substrates that could be employed. In order to overcome this drawback, Parson investigated an elegant way of using ionic liquids to establish milder reaction conditions in Mn(OAc)3-mediated reactions.2 It was shown that ionic liquids, such as l-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), which is miscible with polar solvents (e.g. methanol, dichloromethane) could be used in Mn(OAc)3-mediated radical reactions. 

A notable recent innovation is the coupling of dimethyl acetylenedicarboxylate (DMAD), cyclohexyl isocyanide and an aromatic aldehyde in benzene under reflux giving the 2-aminofurans 70 in good yield (60 70%) (Eq. (9)) (00CC1019, 03ACR899). The method can be carried out at room temperature in higher yield in an ionic liquid (l-butyl-3-methylimidazolium tetrafluoroborate) from which the product is easily isolated by extraction with ether (04S2376). 

It has been reported that palladium-catalyzed cross-coupling can be performed in ionic liquids such as l-butyl-3-methylimidazolium tetrafluoroborate. In this coupling procedure the solvent and catalyst system could be recycled, keeping the same levels of catalyst activity (Scheme 12.70) [155]. 

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