1- Butyl-3-methylimidazolium tetrafluoroborate ionic liquid bmim

In the process of developing the Stetter reaction in ionic liquids, Gree and coworkers applied their methodology to the synthesis of haloperidol (Scheme 25) [101], A variety of aromatic aldehydes react with methyl acrylate 160 when butyl-methylimidazolium tetrafluoroborate [bmim][BF ] is used as solvent. In the synthesis of haloperidol, electron-deficient aldehyde 153 was subjected to standard reaction conditions with 160 to provide 161 in good yield. 

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. 

The related system 31 has been prepared by thionation of the diketone 32 with P4S10 or Lawesson s reagent. Furthermore, dithieno[2,3-6 2 ,3 -c( thiophene 31 was also submitted to electrochemical polymerisation <04TL3405>. Lawesson s reagent has also been used to effect conversion of several 1,4-diketones to thiophenes employing a new reusable catalytic system consisting of Bi(OTf)3 and the ionic liquid [bmim]BF4 (l-butyl-3-methylimidazolium tetrafluoroborate) <04TL5873>. 

Electrooxidative polymerization of pyrrole, thiophene, and aniline was achieved in various imidazolium ionic liquids [26-28]. l-Butyl-3-methylimidazolium tetrafluoroborate and hexafluorophosphate ([BMIM])[BF4] and [BMIM] [PFe]) for electropolymerization and notably 7i-conjugated polymers thus obtained are highly stable, and they can undergo electrochemical doping and dedoping in the ionic liquids up to million cycles. In addition, the polymers have cycleswitching speeds as fast as 100 m. 

The first successful hydrogenation reactions in ionic liquids were studied by the groups of de Souza [45] and Chauvin [46] in 1995. De Souza et al. investigated the Rh-catalyzed hydrogenation of cyclohexene in l-n-butyl-3-methylimidazolium ([BMIM]) tetrafluoroborate. Chauvin et al. dissolved the cationic Osborn complex [Rh(nbd)(PPh3)2][PFg] (nbd = norbornadiene) in ionic liquids with weakly coordinating anions (e.g., [PFg] , [BFJ , and [SbF ] ) and used the obtained ionic catalyst solutions for the biphasic hydrogenation of 1-pentene as seen in Scheme 5.2-7. 

A basic ionic liquid, l-methyl-3-butylimidazolium hydroxide ([bmIm]OH) and l-butyl-3-methyl-methylimidazolium tetrafluoroborate ([bmim]BF4), has been introduced as a catalyst and reaction medium for the Markovnikov addition of imidazoles 116 to vinyl esters 115 under mild conditions to give imidazoesters 117 <06JOC3991 06TL1555>. A series of (nitroimidazolyl)succinic esters and diacids were prepared from the Michael-type addition of the nitroimidazole to the a,P-unsaturated ester <06S3859>. 

One of the important new directions in the study of addition reactions of organozinc compounds to aldehydes is the use of ionic liquids. Usually, application of these compounds in reactions with common organometallic reagents has a serious problem ionic solvents are usually reactive toward them, particularly Grignard and organolithium derivatives. It has been recently reported that carbonyl compounds react with allylzinc bromide formed in situ from allyl bromide and zinc in the ionic liquid 3-butyl-l-methylimidazolium tetrafluoroborate, [bmim][BF4].285 Another important finding is that the more reactive ZnEt2 alkylates aldehydes in a number of ionic liquids at room temperature.286 The best yields (up to 96%) were obtained in A-butylpyridinium tetrafluoroborate, [bpy][BF4] (Scheme 107). 

The electrodeposition of silver from chloroaluminate ionic liquids has been studied by several authors [45-47], Katayama et al. [48] reported that the room-temperature ionic liquid l-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM]BF4) is applicable as an alternative electroplating bath for silver. The ionic liquid [EMIM]BF4 is superior to the chloroaluminate systems since the electrodeposition of silver can be performed without contamination of aluminum. Electrodeposition of silver in the ionic liquids 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) and l-butyl-3-methylimidazoliumhexafluorophosphate was also reported [49], Recently we showed that isolated silver nanoparticles can be deposited on the surface of the ionic liquid Tbutyl-3-methylimidazolium trifluoromethylsulfonate ([BMIMJTfO) by electrochemical reduction with free electrons from low-temperature plasma [50] (see Chapter 10). This unusual reaction represents a novel electrochemical process, leading to the reproducible growth of nanoscale materials. In our experience silver is quite easy to deposit in many air- and water-stable ionic liquids. 

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. 

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. 

As part of their study on gastric (H+/K+)-ATPase inhibitors, Kang et al. developed a simple and convenient synthetic approach to 1,2,3-trisubstituted pyrrolo[3,2-c]quinolines by means of Pd-catalyzed heteroannulation of 4-amino-3-iodoquinoline derivatives with internal alkynes [76]. The following scheme shows an example of a reaction using 4-arylamino-3-iodoquinoline derivative 180 with alkyne 181 to provide 1-arylpyrrolo [3,2-c]quinoline 182, illustrating the possibility of introducing diverse substituents to 1-arylpyrrolo[3,2-c]quinolines. In addition, a Pd-catalyzed domino hydroarylation/ cyclization process was reported to form substituted quinolines [77]. Thus, 3-arylquino-lines were prepared in 56-74% yield when 3,3-diethyl-l-phenyl-1-propyne and aryl iodide were refluxed in ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate [(bmim)BF4 ],in the presence of HCO2H, EtjN, and palladium catalyst. Meanwhile,... 

In view of the rapidly increasing importance of imidazolium-based ionic liquids as novel reaction media, use of 1 -butyl-3 -methylimidazolium tetrafluoroborate ([bmim] [BF ]) as a recyclable solvent and promoter for greener organic synthesis is attracted the attention of many organic chemists. 

Li and coworkers reported their primary results on the Mannich reaction catalyzed by a cation-functionalized acidic ionic liquid, l-carboxymethyl-3-methylimidazo-lium tehafluoroborate ([cmmim][BF ]) in the mixture of water and l-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF ]) (Fig. 12.6) [5]. 3-aminoketone derivatives were synthesized successfully in aqueous [bmim][BF ] with satisfactory to excellent yields, and the catalyst-containing aqueous media can be recycled at least six times with similar activity. In their procedure, the recovered catalyst-containing aqueous media could be reused directly (straightforwardly) without other manipulation such as distillation and dehydration. 

Zhu carried out the cycloaddition of C60 and methanofullerene dihalides, C6o(CX2) (X = Cl, Br, I), with Mg in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM]BF4 with a yield of 55-84%, in contrast to 6-21% yield in THE under sonication (Scheme 4). Only [6,6]-ring junction cycloaddition isomers of C121 were detected, showing the cyclopropane configuration on the connecting C atom. 

The coupling of electron-rich olefins in conventional solvents often requires additives such as silver triflate or thallium acetate to obtain high a/p selectivity. 1-Butyl-3-methylimidazolium tetrafluoroborate ([BMIm]BF4) is an excellent catalytic system for highly regioselective a-arylation of several electron-rich olefins. Butyl vinyl ether 9 reacted with p-bromobenzaldehyde 10 selectively afp ratio >99 1) to 11 (Scheme 15.3 [42]). Comparative experiments in conventional solvents (e.g. DMF) resulted in product mixtures with aip ratios of 46 54 to 69 31. It has been suggested that the ionic pathway is responsible for the unique regiocontrol in the ionic liquid [48-50]. 

Tanaka and his associates demonstrated for the first time how to use non-volatile ionic liquids (ILs) as solvents in palladium-catalyzed carbonylations [163], In the case of alkoxycarbonylation of bromobenzene, higher yields were obtained when 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] was used as the reaction medium compared with standard conditions. And the selectivity for the monocarb-onylation of iodobenzene with t -PrOH or Et2NH was significantly enhanced by [bmim][BF4]. After separation of the products, the solvent-catalyst system was easily recycled and exhibited catalytic activity up to seven times. Since then the replacement of traditional solvents with quaternary ammonium halides, imidazoli-um- or pyridinium-derived ILs has gained increasing importance [164—173]. Recently, the phosphonium salt IL trihexyl(tetradecyl)phosphonium bromide has proven to be an effective reaction medium for various carbonylation reactions of aryl and vinyl bromides or iodides under mild conditions (Scheme 2.17) [174]. 

Figure 11.9 Chemical structure of cation and anion of l-butyl-3-methylimidazolium tetrafluoroborate. The dashed lines illustrate how the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim ][BF4 ]) is decomposed into one CH3 group, three CH2 groups, and one [mim ][BF4 ] group.

Reaction of 3,4-di-ferf-butylthiophene-l-oxide in ionic liquid l-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) with dienophile parasorbic acid afforded the Diels-Alder product 33 in 91% yield. But the resulting oxidation products 34 and 35 showed no significant photoreactivity, rendering it an inappropriate strategy for the synthesis of a two-stage photobase generator (PBG) based on photoinduced aromatization (Scheme 24) [38]. 

Ionic liquids l-ethyl-3-methylimidazolium diethylphosphate EMIMDEP, l-butyl-3-methylimidazolium hexafluorophosphate EMIMPF6, l-hexyl-3-methylitnidazolium chloride HMIMCl, l-butyl-3-methylimidazolium trifluoromethanesulfonate BMIM OTf, l-butyl-3-methylimidazolium tetrafluoroborate EMIMEF4, trihexyltetradecylphosphonium chloride HPCl, and l-butyl-3-methylimidazolium chloride EMIMCl were sup>plied by Alrdich. Composition of a typical elastomer mixture rubber - 100 phr, DCP - 2 phr, TAC - 0.5 phr, ZnO - 5 phr, MET - 2 phr, S - 2 phr, Ionic liquids - 3 phr, filler 20-100 phr. 

The reduction of Pd(acac)2 (acac=acetylacetonate), dissolved in l-n-butyl-3-methylimidazolium hexafluorophosphat [BMIM][PF6] or l- -butyl-3-methylimidazolium tetrafluoroborate[BMIM][BF4] as ionic liquids, by molecular hydrogen (4 atm) at 75 °C affords stable, nanoscale Pd(0) particles with sizes of 4.9+0.8 ntn. In as much as 1,3-butadiene is at least four times more soluble in the l-n-butyl-3-methylimidazolium tetrafluoroborate than butenes, the selective partial hydrogenation could be performed by Pd(0) nanoparticles embedded in the ionic liquid (Umpierre et al., 2005). 

The reaction of NaBH4 with RuCls dissolved in l-n-butyl-3-methylimidazolium hexafluorophosphate [BM1M][PF6] and l- -butyl-3-methylimidazolium tetrafluoroborate [BMIM] [BF4] as ionic liquid is a simple and reproducible method for the synthesis of stable ruthenium oxide nanoparticles with a narrow size distribution within 2-3 nm. These nanoparticles showed high catalytic activity either in the solventless or liquid-liquid biphasic hydrogenation of olefins and arenes under mild reaction conditions. Nanometric ruthenium oxide confined in a zeolitic framework was recently reported as an efficient catalyst for alcohol oxidation under mild aerobic conditions. The nanofjarticles could be reused in solventless conditions up to 10 times in the hydrogenation of 1-hexene yielding a total turnover number for exposed Ru(0) atoms of 175,000 (Rossi et al., 2004 Rossi et al., 2004). 

Sweeny, B. K. D. G. Peters (2001). Cyclic voltammetric study of the catalytic behaviour of nickel(I) salen electrogenerated at a glassy carbon electrode in an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate, BMIM+BF4 . Electrochemistry Communication, Vol.3, No.l2, (December 2001), pp. 712-715, ISSN 1388-2481... 

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