L-Butyl-3-methylimidazolium salts

Prior to the study of Jacobs, Song et al. [87] had already reported monomeric Cr-salen 63 catalyzed ARO of epoxides with TMSN3 in ionic liquid l-butyl-3-methylimidazolium salts [bmim][X]. The ARO reaction proceeded readily at room temperature with easy catalyst/solvent recycling and does not include hazardous workup stages such as distillation of the azide product. 

Aminocarbonylation provides an efficient method for the synthesis of carboxamides from readily available alkenyl halides. This reaction finds many applications in organic synthesis, especially for the introduction of amides with a variety of A -substituents. For example, steroidal alkenyl iodide 137 was transformed to the corresponding amide derivative 138 in 88% yield through aminocarbonylation (Equation (10)). In this reaction, the palladium catalyst was recovered by using an ionic liquid, l-butyl-3-methylimidazolium salt 139, as reaction media, and reused five times with only a minor loss of activity. ... 

Headley, A. D. and Jackson, N. M., The effect of the anion on the chemical shifts of the aromatic hydrogen atoms of liquid l-butyl-3-methylimidazolium salts, /. Phys. Org. Chem., 15, 52, 2002. 

The effective RCM of dienes, catalyzed by ruthenium allenylidene salts [Cl(PCy3)(p-cymene) Ru(=C=C=CPh2)]+(0CF3S02), has been observed in ionic liquid (l-butyl-3-methylimidazolium salts) (Eq. 80) [133]. 

Unlike polarity, the solubility of ionic liquids depends strongly on the structure of the associated anion. In fact, the miscibiUty of ionic liquids with traditional solvents is one of their most interesting features and is clearly observed during the anion metathesis of imidazolium derivatives. The starting chlorine salt, for example [bmim][Cl], is completely soluble in water. After exchange of the anion, [bmim][PF6] or [bmim][NTf2] salts are obtained as hydrophobic products and therefore form a separate layer. Table 2.7 summarizes the solubility of l-butyl-3-methylimidazolium salts as function of the anion. ... 

Study of the Ionic Conductivity of l- -Butyl-3-methylimidazolium Salts as Ionic Liquids. 

Behar, D., Gonzalez, C. Neta, P. (2001). Reaction Kinetics in Ionic Liquids Pulse Radiolysis Studies of l-Butyl-3-methylimidazolium Salts,. Phys. Ghent. A105 7607-7614. 

Ionic liquids, having per definition a melting point below 100 °C, and especially room temperature ionic liquids (RTIL) have attracted much interest in recent years as novel solvents for reactions and electrochemical processes [164], Some of these liquids are considered to be green solvents [165]. The scope of ionic liquids based on various combinations of cations and anions has dramatically increased, and continuously new salts [166-168] and solvent mixtures [169] are discovered. The most commonly used liquids are based on imidazolium cations like l-butyl-3-methylimidazolium [bmim] with an appropriate counter anion like hexafluorophos-phate [PFg]. Salts with the latter anion are moisture stable and are sometimes called third generation ionic liquids. 

Pure ILs have a dual nature since they are actually molten salts or a mixture of cations and anions. They were found to have a relatively high solvent polarity, comparable to that of short-chain alcohols [4-5]. Since CCC needs to work with a Diphasic liquid system, water-insoluble ILs should be selected if an aqueous phase is desired, l-butyl-3-methylimidazolium hexa-fluorophosphate ([C4CiIm][PFg]) has limited water solubility (18 g/L or 1.3% or 63 mM [5]) and is easy to synthesize. It was the first IL used in CCC [6]. 

Carper, W. R., Meng, Z., Wasserscheid, R, and Dolle, A., NMR relaxation studies and molecular modeling of l-butyl-3-methylimidazolium PF, , [BMIMUPF ], International Symposium on Molten Salts, Trulove, P. C., DeLong, H. C., and Mantz, R. A. (Eds), Electrochem. Soc. Proceedings 2002-19 (Molten Salts Xlll), 973-982, 2002. 

The reaction of l- -butyl-3-methylimidazolium chloride (BMIC) with sodium tet-rafluoroborate or sodium hexafluorophosphate produced the room temperature-, air-and water-stable molten salts (BMr)(BF4 ) and (BMTXPFg ), respectively in almost quantitative yield. The rhodium complexes RhCKPPhjls and (Rh(cod)2)(BF4 ) are completely soluble in these ionic liquids and they are able to catalyze the hydrogenation of cyclohexene at 10 atm and 25°C in a typical two-phase catalysis with turnovers up to 6000 (see fig. 6.10). 

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. 

Water soluble Rh/tppts and Rh/tppms complexes dissolved in nonaqueous media such as the ionic liquids, l-ethyl-3-methylimidazolium or l-n-butyl-3-methylimidazolium salt have also been used as catalysts in the hydroformylation of 1-pentene employing a two phase system.15,16 The yields obtained were 16-33% (TOF=59-103 h 1) without any leaching of the rhodium from the ionic liquid to the aldehydes/feedstock phase. Rh/PPh3 catalysts exhibited higher rates (TOF=333 h 1) for the same biphasic reaction albeit with leaching of rhodium due to the uncharged nature of the catalytic system.15... 

Certain quaternary salts of imidazoles have become important as ionic liquids, in particular salts of l-butyl-3-methylimidazolium (bmim). Preparation of imidazolium-containing ionic liquids, in the desired product ionic liquid as a solvent, is a virtually solvent-free, one-pot process proceeding in good to excellent yields <2003S2626>. There are also microwave-assisted, solvent-free processes for the preparation of imidazolium-based ionic liquids <2001CC643, 2003GC181>. 

Ionic liquids have also been used as reaction media (Box 9). The high polarity of quaternary ammonium salts is exploited to favour polar reaction steps. For example, with l- -butyl-3-methylimidazolium tetrafluoborate, 2,7-octadien-l-ol (Section 5.4.3) was obtained in good yield from butadiene and water and was readily separated as it was immiscible with the ionic liquid below 5°C [J. E. L. Dullius, P. A. Z. Suarez, S. Einloft, R. F. deSouza, J. Dupont, J. Fisher and A. DeCian, Organometallics 1998, 17, 815]. 

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. 

The fluorescent probe 4-aminophthalimide (63) as well as its /V,/V-diethyl homomorph (89) were used by Samanta and coworkers148 149 to study the polarity and fluorescence dynamics in l-alkyl-3-methylimidazolium salts. The alkyl groups were variously ethyl, butyl and octyl and the anions were nitrate, tetrafluoroborate, hexafluorophosphate and bis(triflyl)imide. Similar conclusions were reached concerning the effects of alkyl chain length and anion as those obtained by Carmichael and Seddon142 using Nile Red. The solvation dynamics were found to depend on the viscosity of the media. Further use of 63 in l-butyl-3-methylimidazolium hexafluorophosphate was reported by Ingram and... 

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