Ionic liquids, l-butyl-3-methylimidazolium

Alammar and Mudring [17] have also synthesized ZnO in the form of nanorods with lengths from 50-100 nm and diameters of about 20 nm (Fig. 8.5.) using the ionic liquid l-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide, [C4mim][Tf2N]. 

Even though Ti02-based materials have been far more investigated than any other photocatalyst and this chapter is dedicated to these systems, it is important at least to mention here some of the promising alternative materials studied for wastewater treatment. CdS hollow nanospheres were prepared in a single-step hydrothermal route by Li et al. [109] using the ionic liquid l-butyl-3-methylimidazolium... 

Scheme 6.93) [192]. Using either of the two solvent systems, all studied cycloaddition reactions were completed in less than 1 min upon microwave irradiation at 50 °C employing 3 mol% of the catalyst. An additional advantage of using the ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) as solvent is that it facilitates catalyst recycling. 

Inter- and intramolecular hetero-Diels-Alder cycloaddition reactions in a series of functionalized 2-(lH)-pyrazinones have been studied in detail by the groups of Van der Eycken and Kappe (Scheme 6.95) [195-197]. In the intramolecular series, cycloaddition of alkenyl-tethered 2-(lH)-pyrazinones required 1-2 days under conventional thermal conditions involving chlorobenzene as solvent under reflux conditions (132 °C). Switching to 1,2-dichloroethane doped with the ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) and sealed-vessel microwave technology, the same transformations were completed within 8-18 min at a reaction temperature of 190 °C (Scheme 6.95 a) [195]. Without isolating the primary imidoyl chloride cycloadducts, rapid hydrolysis was achieved by the addition of small amounts of water and subjecting the reaction mixture to further microwave irradia-... 

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. 

In order to overcome the difficulties associated with the covalent hydrates, anhydrous reagent systems have been investigated, including ionic liquids <2004S2809> and NBS in tetrabutylammonium bromide <200581103>. For example, the bromination of 2-aminopyrimidine 61 with the ionic liquid l-butyl-3-methylimidazolium tribromide [(bmim)Br3] gave 2-amino-5-bromopyrimidine 62 in 96% yield after 5 min at — 10°C <2004S2809>. 

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. ... 

Zafarani-Moattar, M.T. and Shekaari, H. Volumetric and speed of sound of ionic liquid, l-butyl-3-methylimidazolium hexafluorophosphate with acetonitrile and methanol at T = (298.15 to 318.15) K, /. Chem., Eng. Data, 50,1694,2005. Wang, J. et al.. Excess molar volumes and excess logarithm viscosities for binary mixtures of the ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate with some organic solvents, /. Solution Chem., 34, 585, 2005. 

Fletcher, K.A., Pandey, S., Storey, I.K., Hendricks, A.E., and Pandey, S., Selective fluorescence quenching of polycyclic aromatic hydrocarbons by nitromethane within room temperature ionic liquid l-butyl-3-methylimidazolium hexafluoro-phosphate. Anal. Chim. Acta, 453, 89-96, 2002. 

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. 

Polyakova, Y., Jin, Y., Zheng, J., and Row, K. H., Effect of concentration of ionic liquid l-butyl-3-methylimidazolium tetrafuoroborate for retention and separation of some amino and nucleic acids, /. Liq. Chromatogr., 29, 1687-1701, 2006. 

Wang, J.-H., Cheng, D.-H., Chen, X.-W., Du, Z., Fang, Z.-L., Direct extraction of double-stranded DNA into ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate and its quantification. Anal. Chem., 79, 620-625, 2007. 

Antony, J. H., Mertens, D., Dolle, A. et al.. Molecular reorientational dynamics of the neat ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate by measurement of nuclear magnetic relaxation data., ChemPhysChem., 4, 588, 2003. 

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). 

A new ionic liquid, l-butyl-3-methylimidazolium tribromide can act as an oxidizing agent to convert alcohols to aldehydes and ketones.338 In the case of benzyl alcohols and diols, [Bmim][Br3] combines oxidizing and brominating properties in a one-pot synthesis of /3-bromoethyl esters. 

M. Eckstein, P. Wasserscheid, and U. Kragl, Enhanced enantioselectivity of lipase from Pseudomonas sp. at high temperatures and fixed water activity in the ionic liquid, l-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide, Biotechnol. Lett. 2002b, 24, 763-767. 

Anthony, J. L., Maginn, E. J., Brennecke, J. F. (2002), Solubilities and Thermodynamic Properties of Gases in the Ionic Liquid l- -Butyl-3-methylimidazolium Hexafluorophosphate, J. Phys. Chem. B 106, 7315-7320. 

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]. 

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]. 

Berthod, A. and Carda-Broch, S. 2004. Use of the ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate in countercurrent chromatography. Analytical and Bioanalytical Chemistry, 380 168-77. 

Sneddon s group investigated AB dehydrogenation in the ionic liquid l-butyl-3-methylimidazolium chloride (bmimCl) with an AB content of 50% [110]. Because of the low solubility of AB in bmimCl, one can assume that this system was essentially heterogeneous in nature. Similarly to the solid nanocomposites the change in the reaction environment induces several positive effects on the A B decomposition, such as an increase in the reaction kinetics, the absence of an induction period, a strong reduction in the borazine emissions, and with 1.6 equiv of H 2 at 98 °C in contrast to... 

Ethyl diazoacetate is a frequently encountered carbene donor for the methylenation of imines. For example, the imine derived from -chlorobenzaldehyde 589 is converted to the tfr-aziridinyl ester 590 upon treatment with ethyl diazoacetate in the presence of lithium perchlorate <2003TL5275>. These conditions have also been applied to a reaction medium of the ionic liquid l- -butyl-3-methylimidazolium hexafluorophosphate (bmimPF6) with excellent results <2003TL2409>. An interesting enantioselective twist to this protocol has been reported, in which a diazoacetate derived from (iJ)-pantolactone 591 is used. This system was applied to the aziridination of trifluoro-methyl-substituted aldimines 593, which were prepared in situ from the corresponding aminals 592 under the catalysis of boron trifluoride etherate to give aziridines 594 (Scheme 143) <2003TL4011>. 

Transformations of oxiranes into thiiranes by reaction with potassium thiocyanates, carried out in mixtures of ionic liquids (l-butyl-3-methylimidazolium hexafluorophosphonate ([bmim]PF6) or tetrafluoroborate ([bmim]BF4) and water (2 1), gave the corresponding thiiranes in very good yield (up to 96% Equation 56) <2003JOC2525>. The ionic liquid may be reused after extraction of products with ether for example, treatment of 2-phenyloxirane with potassium thiocyanate in [bmim]PF6 ionic liquid afforded 2-phenylthiirane in 93%, 89%, 85%, 81%, and 78% yields over five cycles. 

Multicomponent reactions have been described for several syntheses of imidazoles. Highly efficient methods for the syntheses of spiroimidazolinones via microwave-assisted three-component one-pot sequential reactions or one-pot domino reactions have been described <06JOC3137>. Multicomponent reactions between 2-aminopyrimidine, aldehydes and isonitriles afforded imidazo[l,2-a]pyrimidines <06TL947>. Two novel one-step microwave mediated syntheses of arrays of 3-iminoaryl-imidazo[l,2-a]pyridines and imidazo[l,2-a]pyridyn-3-ylamino-2-acetonitriles were synthesized by multicomponent reactions under microwave condition in methanol by simply mixing a-aminopyridines, aldehydes, and trimethylsilylcyanide catalyzed by polymer-bound scandium triflate <06TL2989>. 3-Aminoimidazo[l,2-a]pyridines have been synthesized via the multicomponent reaction of aldehydes, isocyanides and 2-aminopyridines in the presence of the ionic liquid l-butyl-3-methylimidazolium bromide [bmim]Br<06TL3031>. 

Emel yanenko V N, Verevkin S P, Heintz A. The gaseous enthalpy of formation of the ionic liquid l-butyl-3-methylimidazolium dicyana-mide from combustion calorimetry, vapor pressure measurements, and Ab initio calculations. J. Am. Chem. Soc. 2007. 129, 3930-3937. 

Harris KR, Woolf LA, Kanakubo M (2005) Temperature and pressure dependence of the viscosity of the ionic liquid l-butyl-3-methylimidazolium hexafluorophosphate. J Chem Eng Data 50 1777-1782... 

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). 

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