Hmim, ionic liquid

Davis and co-workers have carried out the first examples of the Knoevenagel condensation and Robinson annulation reactions [61] in the ionic liquid [HMIM][PFg] (HMIM = l-hexyl-3-methylimidazolium) (Scheme 5.1-33). The Knoevenagel condensation involved the treatment of propane-1,3-dinitrile with a base (glycine) to generate an anion. This anion added to benzaldehyde and, after loss of a water molecule, gave l,l-dicyano-2-phenylethene. The product was separated from the ionic liquid by extraction with toluene. 

The Robinson annulation of ethyl acetoacetate and trans-chalcone proceeded smoothly to give 6-ethoxycarbonyl-3,5-diphenyl-2-cyclohexenone in 48 % yield. The product was separated from the ionic liquid by solvent extraction with toluene. In both these reactions, the ionic liquid [HMIM][PF6] was recycled and reused with no reduction in the product yield. 

The use of the ionic liquid [bmim][BF4] further improved the Burgess epoxidation system [70]. Chan and coworkers found that replacement of sodium bicarbonate for tetramethylammonium bicarbonate and performing the reaction in [hmim][BF4] allowed for efficient epoxidation of a number of different olefins, including substrates affording acid-labile epoxides (such as dihydronaphthalene (99% yield) and 1-phenylcyclohexene (80% yield)). 

Goharshadi EK, Ding Y, Jorabchi MN, Nancarrow P (2009) Ultrasound-assisted green synthesis of nanocrystalline ZnO in the ionic liquid [hmim][NTf2]. Ultrason Sonochem 16 120-123... 

One large scale application of an ionic liquid is as a base to remove HC1 during the preparation of alkoxyphenylphosphines. BASF use N-methy limidazole which forms the ionic liquid [Hmim]Cl and forms a second liquid layer that may easily be removed from the system and recycled via phase separation. Although the ionic liquid is not employed as a solvent, the process makes use of biphasic technology to give a more efficient process which avoids an inconvenient filtration step. 

Bronsted acidic ionic liquids [HMIM]BF4, [HMIM]TfO, and [HMIM]TsO are effective for proton- and metal-assisted catalytic processes such as the dimerization of methyl acrylate and ring-closure metathesis (Scheme 3) (72J). For example, the acidic [HBIM]BF4 in association with the [Ru( = C = C = CPh2)(/ -cymene) (PCy3)Cl][OTf catalyst afforded a dramatic increase in the activity (100%) and selectivity (100%) for the ring-closure metathesis of A,A-diallyltosylamide. 

The Diels-Alder reaction between cyclopentadiene (1) and a series of dienophiles (2), Scheme 5, was examined in a typical alkylimidazolium ionic liquid at room temperature l-hexyl-3-methylimidazoliumtetrafluoroborate, [hmim][BF4]. ... 

Gomes de Azevedo, R. et al.. Thermophysical and thermodynamic properties of ionic liquids over an extended pressure range [bmim][NTf2] and [hmim] [NTiilJ. Chem. Thermodyn., 37, 671, 2005. 

Shiflett MB, Yokozeki A (2007) Solubility of C02 in room temperature ionic liquid [hmim][Tf2 N], J Phys Chem B lll(8) 2070-2074... 

One interesting application of an ionic liquid does not involve its use as a solvent. The company BASF used N-methylimidazole to scavenge the HC1 formed in the reaction of dichlorophenyl phosphine with ethanol (Fig. 7.33). This results in the formation of N-methylimidazoliumchloride (Hmim-Cl), which has a... 

Catalytic asymmetric Diels-Alder reactions in ionic liquids, using an air- and moisture-stable chiral BlNOL-indium complex prepared from ( S)-BINOL and InClj, have also reported [46]. The reactions of various dienes with 2-methacrolein or 2-bromoacrolein proceeded in an ionic hquid with good yields and excellent enantioselectivities (up to 98% ee). The chiral In(lll) catalyst immobilized in ionic liquid [hmim][PF 5] could be reused seven times without any significant loss in catalytic activity (Scheme 7.13). 

Besides, Shen et al. [26] have performed comparative studies on alkylation of phenol with ferf-butyl alcohol (TBA) with liquid acids such as H PO or solid acids, for example, HZSM-5, H-(), dodecatungstophosphoric acid (HPW), and HPW/ MCM-41, in the ionic liquids [BMIM]PFg, [OMIM]BF ([OMIM] = 7-octyl-5-methylimidazolium cation), and [HMIM]BF ([HMIM] = 7-hexyl-5-methylimidazo-lium cation). The results suggested that ionic liquids improve the catalytic activity of HjPO, with the conversion of phenol increasing from 44.5% to the maximum value of 77.3% in the alkylation of phenol with TBA by H PO in different ionic liquids. This improvement effect in conversion may be attributed to the higher solubility of... 

Rahmati-Rostani M, Ghotbi C, Hosseini-Jenab M et al (2009) Solubility of H S in ionic liquids [hmim][PFJ, [hmim][BFJ, and [hmimllTf N]. J Chem Thermodyn 41 1052-1055... 

The storage stability of CaLB in [bmim ][PF "], [hmim ][PF ], [omim ][PF ], [hmim [NT -], [htnim [BF -] and [bmim ][dca ] was studied by de los Pros et al. [12]. They found the most important effect on CaLB stability by changing the nature of IL anions. For the ionic liquids containing the cation [bmim ], the increase in half-life time was in the order [bmim ][dca ]<[bmim ][PFg ], and for those containing thecation [hmim+], the order was [hmim ][BF ] < [hmim ][NTfj ] < [hmim ]... 

Ionic liquids have also been used as reaction media in biocatalytic esterification reactions. In this context, the enantioselective esterification of 2-substituted-pro-panoic acids with 1-butanol catalysed by CrL in ionic liquids has been carried out by Ulbert et al. [76] (Fig. 7.10). It was demonstrated that application of [hmim+] [PF ] and [onim ][PF ] ionic hquids was beneficial from not only enzyme activity... 

Temperature stability is important for some applications of SILMs in gas separation, such as capture of CO from coal gasification plants. Ilcovich et al. [25] analysed the stability of a SILM based on [hmim+lfNTfj ] supported on a polysulphone organic membranes in the selective separation of CO from He at high temperature. This membrane was found to be stable up to 125 C, the failure of the membranes above that temperature being attributable to support failure rather than any effect on the ionic liquid. Recently, Myers et al. [32] reported operation of [hmim ][NTfj ] supported on nylon membranes up to 300 C. It was found that permeability in this [hmim [NTfj ] membrane increased with temperature while the selectivity decreased. 

SO.,"] < [MeSO.,"] [40]. These results were quite encouraging and suggested that these SLMs based on ILs could be used for the selective separation of the organic esters from the reaction mixture. SILMs can also be used for the separation of aromatic hydrocarbons from aliphatic hydrocarbons. In this context, the selective separation of benzene, toluene and p-xylene from n-heptane was achieved using SILMs based on [bmim ][PE "], [hmim+][PFg ], [omim+][PFg ] and [Et MeMoEtN [TfjN"] supported on a polyvinyhdene fluoride manbrane [9]. It was found that aromahc hydrocarbons were successfully transported through the membrane based on these ionic liquids, and the maximum selectivity to n-heptane was when benzene used in the aromatic permeation and [bmim+][PFg ] was taken in the hquid membrane phase. 

Scovazzo et al. [24] explored the selective separation of the gas pairs CO /CH and COj/N nsing continnons flow of the mixed gases nsing [emim][BF ] [emim ][TfO ] and [emim+][dca ] snpported on hydrophilic PVDF and [emim+][Tf2N ], [hmim ] [Tf N ] and [emim+][BETl ] snpported in a hydrophilic PES membrane. The highest CO /CFl and CO /N selectivities were 27 and 21.2 nsing the ionic liquids [emim+][BE ] and [emim+JlTf N ], respectively. 

They showed that the oxidation of primary alcohols to their corresponding aldehydes can be completed by nsing lower amounts of VOCacac) and DABCO at higher temperature (90°C). When Cn(II) 2-ethylhexanoate (2 mol%) was added to the reaction mixture and [hmim][OTf] was nsed as ionic liquid, carboxylic acids were formed as the only products of the oxidation reactions. These catalytic systems could also be recycled and reused for three runs without any significant loss of catalytic activity. 

Br0nsted acidic ionic liquids have been successfully applied to a variety of reactions including esterification of carboxylic acids [55], protection of aldehydes and ketones [56], and cleavage of ethers [57], 3-Methylimidazolium hydrogen sulfate ([hmim][HSO ]) is a Brpnsted acidic ionic liquid that applied for the oxidation of... 

Wu HH, Yang F, Pg C, Tang J, He MY (2004) An efficient procedure for protection of carbonyls in Brpnsted acidic ionic liquid [hmim][BFJ. Tetrahedron Lett 45 4963-4965... 

In pyridinium chloride ionic liquids and in l,2-dimethyl-3-hexylimidazolium chloride ([HMMIMJCl), where the C(2) position is protected by a methyl group, only [PdCl4]2- was observed, whereas in [HMIM]Cl, the EXAFS showed the formation of a bis-carbene complex. In the presence of triphenylphosphine, Pd-P coordination was observed in all ionic liquids except where the carbene complex was formed. During the Heck reaction, the formation of palladium was found to be quicker than in the absence of reagents. Overall, the EXAFS showed the presence of small palladium clusters of approximately 1 nm diameter formed in solution. 

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