Imidazohum, 1 -methyl-3-

DMII = N,N-dimethyl imidazohum iodide DEII = N,N-diethyl imidazohum iodide BMII = N-butyl-N-methyl imidazohum iodide [Etpy]I = N-ethyl pyridinium iodide [pyMe]I = N-methyl pyridinium iodide MTOPI = methyl trioctyl phosphonium iodide [BusPMe] = methyl tributyl phosphonium iodide. 

In 2006, Xu and Xia et al. revealed the catalytic activity of commercially available D-camphorsulfonic acid (CS A) in the enantioselective Michael-type Friedel-Crafts addition of indoles 29 to chalcones 180 attaining moderate enantiomeric excess (75-96%, 0-37% ee) for the corresponding p-indolyl ketones 181 (Scheme 76) [95], This constitutes the first report on the stereoselectivity of o-CSA-mediated transformations. In the course of their studies, the authors discovered a synergistic effect between the ionic liquid BmimBr (l-butyl-3-methyl-l/f-imidazohum bromide) and d-CSA. For a range of indoles 29 and chalcone derivatives 180, the preformed BmimBr-CSA complex (24 mol%) gave improved asymmetric induction compared to d-CSA (5 mol%) alone, along with similar or slightly better yields of P-indolyl ketones 181 (74-96%, 13-58% ee). The authors attribute the beneficial effect of the BmimBr-D-CSA combination to the catalytic Lewis acid activation of Brpnsted acids (LBA). Notably, the direct addition of BmimBr to the reaction mixture of indole, chalcone, d-CSA in acetonitrile did not influence the catalytic efficiency. 

Henry s law constants, 698 hydrogen peroxide determination, 629, 638 hydroperoxide determination, 678 Al-Ethyl-Al-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxyanUine, 632, 634 Al-Ethyl-Al -methyl imidazohum (emim), transition metal peroxides, 1083 Ethyl plakortide Z, namral occurrence, 610... 

Figure 15.6 Relationship between Jsc and viscosity of the redox medium containing 0.9 M DMHi-i, 50 mM iodine. Organic soivents AN acetonitrile MPN methoxypropionitrile NMO N-methyloxazoiidinone TMS sulfolane. Ionic liquids EMI 1-ethyl-3-methylimidazoHum TMPA trimethylpropylammonium, THA tetrahexylammonium, HMI-I l-hexyl-3-methyl-imidazoHum-iodide, TFSI bis(trifluoromethyl-sulfonyl)imide [21]. (Reprinted by permission of the Publisher, The Electrochemical Society of Japan).

In a theoretical and experimental study, McGuinness et al. described the oxidative addition of an imidahnm cation to zerovalent d metals [23] and came to the conclusion that addition on chelated Pd(0) is favoured over linear [PdCPRj) ] complexes and that C -X (X = I, Br, I) activation on the imidazohum cation is much easier than C -H and C -Me activation with the methyl group beeing the least reactive. 

Yeon S H, Kim K S, Choi S, et al. Physical and electrochemical properties of l-(2-hydroxyethyl)-3-methyl imidazohum and N-(2-hydro-xyethyl)-N-methyl morpholinium ionic hquids. Electrochim. Acta. 2005. 50, 5399-5407. 

Liu Y-Y, Lou W-Y, Zong M-H et al (2005) Increased enantioselectivity in the enzymatic hydrolysis of amino acid esters in the ionic liquid l-butyl-3-methyl-imidazohum tetrafluo-roborate. Biocatal Biotransform 23 89-95... 

Shaabatii A, Farhangi E, Rahmati A (2008) Aerobic oxidation of alkyl arenes and alcohols using cobalt(Il) phthalocyanine as a catalyst in l-butyl-3-methyl-imidazohum bromide. Appl Catal A Gen 338 14-19... 

Ionic liquids are a class of novel solvents with a melting point below 100°C and a negligible vapor pressure, which are interesting entrainers for extractive distillation. Examples of ionic liquids that have been investigated with respect to their potential as entrainers are l-R-3-methyl-imidazoHum-bis(trifluoromethyl-sulfonyl)-imides ([RMIM]+[CE3S02]2N-). 

If ILs are to be used in metal-catalyzed reactions, imidazoHum-based salts may be critical due to the possible formation and involvement of heterocyclic imidazo-lylidene carbenes [Eqs. (2)-(4)]. The direct formation of carbene-metal complexes from imidazolium ILs has already been demonstrated for palladium-catalyzed C-C reactions [40, 41]. Different pathways for the formation of metal carbenes from imidazolium salts are possible either by direct oxidative addition of imidazolium to the metal center in a low oxidative state [Eq. (2)] or by deprotonation of the imidazolium cation in presence of a base [Eq. (3)]. It is worth mentioning here that deprotonation can also occur on the 4-position of the imidazolium [Eq. (4)]. The in-situ formation of a metal carbene can have a beneficial effect on catalytic performances in stabilizing the metal-catalyst complex (it can avoid formation of palladium black, for example). However, given the remarkable stability of this imidazolylidene-metal bond with respect to dissociation, the formation of such a complex may also lead to deactivation of the catalyst This is probably what happens in the telomerization of butadiene with methanol catalyzed by palladium-phosphine complexes in [BMIMj-based ILs [42]. The substitution of the acidic hydrogen in the 2-position of the imidazolium by a methyl group or the use of pyridinium-based salts makes it possible to overcome this problem. Phosphonium-based ILs can also bring advantages in this case. 

Methylation at the 2-position of the imidazolium ring also results in an increase in the stability of imidazoHum-based ILs [13], This is probably best explained by the addition of an electron-donating substituent leading to a reduction in the electro-philicity of the a-carbons of the alkyl chains. 

As ILs are nonvolatile, products can also be isolated be means of distillation. Alternatively, a reduced pressure can be applied to remove volatile products such as water or low alcohols, driving the reaction toward product formation. The latter technique was demonstrated by Itoh and co-workers, who continuously removed methanol from the transesterification of a methyl ester in [BMIM][PF ] [15]. The reaction was catalyzed by the B-lipase from Candida antarctica (CaLB). Itoh s group also most recently identified [BMMIM)[BF4] (BMMIM = l,2-dimethyl-3-butyl-imidazoHum) to be an excellent solvent for setting up a lipase-recycling system using vinyl acetate as the acyl donor [16]. The lipase was used 10 times here without loss of reactivity and enantioselectivity. 

Verevkin, S. P. Vasiltsova, T. V. Bich, E. Heintz, A. Thermodynamic properties of mixtures containing ionic hquids. Activity coefficients of aldehydes and ketones in l-methyl-3-ethyl-imidazohum bis(trifluoromethyl-sulfonyl) imide using the tnmspiration method Fluid Phase Equilib. 2004,275, 165-175... 

Zhang DP, Liu QH, Shi XS, Li YD. Tetrabutylammonium hexafluorophosphate and l-ethyl-3-methyl imidazohum hexafluorophosphate ionic liquids as supporting electrolytes for non-aqueous vanadium redox flow batteries. J Power Sources 2012 203 201-5. 

A group at Exxon immobilized an ionic liquid phase ([BMIM][PFg]) onto modified silica gel (Figure 7.18) [108]. The ionic liquid phase hosted the catalyst HRh(CO)(tppti)3 (tppti = tri(m-sulfonyl)triphenyl phosphine tris(l-butyl-3-methyl-imidazohum)) as well as the excess of noncoordinated ligand. In the hydroformylation of 1-octene, lower activities of the biphasic system in comparison to the simple supported IL system were noted. This was explained by a higher concentration of the active rhodium species at the interface and the... 

Additives such as methyl acetate (MA), toluene, and y-butyrolactone (GBL) have been studied for their effects on capacity and cycleabiUty [17, 129]. Only toluene improves both the initial capacity and cycleability owing to its capabiHty of forming a stable electrode/electrolyte interface [124, 129]. ImidazoHum salts, when introduced into the mixed DME-DOL electrolytes, are reported to improve the cycleability by enhancing the electrochemical reaction of polysulfides and improving the stability of the lithium negative electrode [122]. Addition of tetrabutylam-monium hexafluorophosphate (TBAPFg) into the electrolyte shows a comparable effect [113]. 

Wadhawan JD, Schroder U, Neudeck A, Wilkins SJ, Compton RG, Marken F, Consorti CS, de Souza RF, Dupont J (2000) Ionic liquid modified electrodes. Unusual partitioning and diffusion effects of Fe(CN)64-/3- in droplet and thin layer deposits of l-methyl-3-(2,6-(S)-dimethylocten-2-yl)-imidazohum tetrafluoroborate. J Electroanal Chem 493(1—2) 75—83. doi 10.1016/80022-0728(00)00308-9... 

Smith, G.P., Dworkin, A.S., Pagni, R.M., and Zingg, S.P., Bronsted superacidity of HCl in a liquid chloroaluminate. AlCl3-l-ethyl-3-methyl-lH-imidazohum chloride,/. Am. Chem. Soc., Ill, 525, 1989. 

Fig. 36. Surface tension vs. IL molar fraction for three aqueous systems with l-alkyl-3 methyl-imidazohum halogenated.

We present in this work all pubhshed data on density, refractive index, viscosity, electrical conductivity and surface tension for all systems IL + water and + ethanol covering a broad range of concentrations. For density, refractive index and viscosity the data for mixtures with water or ethanol are very similar, and also their behaviour with concentration is not really dependent of the IL mixed with any solvent (except for its value). Density and refractive index can be deduced one from another using Newton s model, which demonstrates the close relationship between both magnitudes. For electrical conductivity and surface tension, the solvent nature determines the data behaviour obtained. Thus, the electrical conductivity value of the pntre IL for aqueous systems increases up to 10 times, while that increase is halved for ethanol systems. In the case of surface tension the behaviour is completely different depending on the solvent and IL studied. For alkyl-methyl-imidazolium tetrafluoroborate the IL acts like a surfactant in water, and the surface tension value decreases sharply from that of water to that of the pure IL for small concentrations of this last, effect that does not appear for halogenated imidazohum ILs. If we change the water for ethanol, that surfactant like effect disappear, and the surface tension value of the only four ILs measured decreases linearly with the ethanol content down to a common value at about equimolar mixture, and then all data has the same value. 

Seth, D. Chakraborty, A. Setua, P. Sarkar, N. (2007a). Interaction of ionic liquid with water with variation of water content in l-butyl-3-methyl-imidazohum hexafluorophosphate ([brnim][PF6])/TX-100/water ternary microemulsions monitored by solvent and rotational relaxation of coumarin 153 and coumarin 490. J. Chem. Fhys., 126,224512... 

In 2007, Cassol et al., found that the selectivity on the extraction of a specific aromatic compound is influenced by anion volume, hydrogen bond strength between the anion and the imidazohum cation and the length of the l-methyl-3-alkylimidazolium alkyl side chain. The interaction of alkylbenzenes and sulfur heterocyles with the IL is preferentially through CH-tt hydrogen bonds and the quantity of these aromatics in the IL phase decreases with the... 

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