Dimethylimidazolium iodide

To l-methyl-3-ethyIimidazolium bromide (0.1 g) in dry methanol (5 ml) is added silver tetraphenylborate (0.2 g) in methanol (15 ml). The mixture is refluxed (2h) and filtered from silver bromide, and then the solvent is evaporated to give the tetraphenylborate salt (36%), m.p. 140°C. Similarly prepared using silver perchlorate in dry acetone is l-cthyl-3-methylimidazolium perchlorate (83%) as an oily liquid. 

Similar methods apply, and mixtures of products result when the original substrate is substituted in the fused benzene ring. Quatemization is more difficult because benzimidazole is less basic than imidazole. When 5(6)-substituted benzimidazoles are alkylated the product ratios depend on the resonance electronic effects of the substituent, e.g. methylation of 5(6)-nitrobcnzimidazolc gives a 1 1 ratio of 1,5 and 1,6 isomers. Substituents in the 4(7)-positions have increased electronic directing effects, and steric effects also come into play, e.g. methylation of 4(7)-nitrobenzimidazole in basic medium gives a 6 1 ratio of 1,4 to 1,7 isomers. And so, in designing a synthetic approach to a 1-alkyl-C-nitrobenzimidazole, aU of these factors need to be taken into account. It may be more valid to nitrate a 1-alkylbenzimidazole than to alkylate a C-nitrobenziinidazole [2]. 

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Normally acylation reactions would be considered standard chemistry but replacing an aryl bromide with a ketone under relatively mild conditions warrants attention. Here 23 is treated with 1,3-dimethylimidazolium iodide (1,3-dii) in refluxing THE leading to the formation of the ketone 24 (Equation 8) <1997H(45)2159>. 

In a dry, 500-mL, round-bottomed flask, equipped with a magnetic stirrer and a drying tube are placed 44.8 g (0.20 mol) of 1,3-dimethylimidazolium iodide (Note 1), 35.0 g (0.25 mol) of anhydrous potassium carbonate, 6.5 g (0.20 mol) of sulfur (Note 2) and 300 mL of methanol (Note 3). The mixture is stirred for 40 hr at room temperature. The cloudy yellow mixture is filtered through a pad of Cellte (Note 4) and the filter cake is washed with 80 mL of dichloromethane. The combined mother liquor and wash is evaporated to dryness on a rotary evaporator. The orange residue is dissolved in 500 mL of hot water and the hot solution is filtered to remove Insoluble impurities. The aqueous filtrate is reheated and the product crystallizes on cooling. The white needles are collected by filtration, washed with 50 mL of cold water and air dried for 1 hr. The mother liquor is concentrated to yield a second crop of crystals to give a total of 15-16 g (58-62%) of pure 1,3-dimethylimidazole-2-thione, mp 182-183.5°C (Note 5). 

Thin-layer chromatography on alumina,271 silica gel,139,271>272 cellulose,262,272 Avicel,250,262 and polyamide273 thin layers has extended considerably the applications of chromatography to the separation and purification of imidazoles. Polyamide layers are useful especially for the separation of imidazoles and their 1-methyl derivatives and (using methyl ethyl ketone as solvent) allows separation of the more polar co mpounds su ch as 1,3 -dimethylimidazolium iodide.2 7 3 Imidazolines have also been separated by thin-layer chromatography.274... 

Friedel-Crafts reaction of arenes with a-chloro-a-(methylthio)acetophenones [19], When A -phenylbenzimidoyl chlorides are aroylated with an aryl halide in the presence of a catalytic amount of an azoliuni salt (such as 1,3-dimethylimidazolium iodide) and sodium hydride, followed by acid treatment in TUF, unsymmetrical benzils can be isolated in 80-92% yields [201. Added to this method is the sequence ketone enaminoketone a-diketone, which cleaves a carbon-carbon double bond in the final stage by photooxygenation [21]. 

Chlorocinnoline (50) gave 4-benzoylcinnoline (51) [PhCHO, p-MeCeH4-S02Na, 1,3-dimethylimidazolium iodide (catalyst), Me2NCHO, 80°C, 10 min 73% when the sulfinate was omitted, the yield was 39% this suggests that the reaction proceeds better via an intermediate sulfone] several substituted-benzoyl analogs were made similarly. ... 

The reaction of 1,3-dimethylimidazolium iodide (shown below) with one equivalent of KO Bu in THF, followed by addition of one equivalent of Ru3(CO)i2 leads to product A. The IR spectrum of A has several strong absorptions between 2093 and 1975 cm", and the solution H NMR spectrum of A exhibits singlets at 6 7.02 and 3.80 ppm (relative integrals 1 3). (a) What role does KO Bu play in the reaction (b) What is the likely identity of A (c) Draw a possible structure of A and comment on possible isomers. 

The reaction of 1,3-dimethylimidazolium iodide (shown on the next page) with one equivalent of... 

NHC has also been used successfully for the construction of quinoxaline framework in one pot (Scheme 60). The synthesis of 2,3-diarylquinoxalines by the aroylation of N-phenylbenzimidoyl chlorides wi aromahc aldehydes and diamines catalyzed by 3mol% of 1,3-dimethylimidazolium iodide (NHC precursor) has been described by Suzuki et al. [85]. The substrates of the catalytic reaction, i.e., N-phenylbenzimidoyl chlorides, are easily obtained... 

The carbene of l,3-dimethylimidazolium iodide can be generated using sodium hydride. In the presence of a benzaldehyde... 

A simple NHC, A,A -dimethylimidazolium iodide, catalyses a mild aroylation of 3,5-dichloro-2(l/f)pyrazinones (174) at the 2-position, using an aryl or heteroaryl aldehyde. ... 

Liquid l,3-dihexyl-2-iodo-4,5-dimethylimidazolium iodide (XEZREB). A series of related materials were all found to contain water of crystallisation. 

An electrospun membrane was prepared from a 16 wt% solution of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) in a mixture of acetone/AA -dimethylacetamide (7 3 wt%) at an applied voltage of 12 kV [90]. The electrospun membrane was then activated by immersing it in 0.6 M l-hexyl-2,3-dimethylimidazolium iodide, 0.1 M Lil, 0.05 M I2, and 0.5 M 4-tert-butylpyridine in ethylene carbonate/propylene carbonate (1 1 wt%) to obtain the corresponding membrane electrolyte with an ionic conductivity of 10 S cm at 25 °C. On the basis of this electrospun membrane electrolyte, quasi-solid-state dye-sensitized solar cells were fabricated, which showed an open-circuit voltage of 0.76 V, a All factor of 0.62, and a short-circuit current density of 15.57 mA cm at an incident... 

This electrolyte was used to assemble a DSSC, in combination with the Z-907 dye, showing = H-3 mA cmVoc = 0.66 V and FF = 0.71, respectively, yielding an overall energy conversion efficiency of 5.3%. Comparing this electrolyte with the one prepared without polymer, the authors observed that the presence of polymer had no adverse effect on the conversion efficiency. Since the main component of the gel is the ionic liquid, liquid channels are formed in the polymeric phase and the diffusion of iodide and triiodide occurs in these channels." A similar phenomenon was also observed in other polymer gel systems." " Similar electrolytes based on l-propyl-2,3-dimethylimidazolium iodide containing 5 wt% of PVDF-HFP (5 wt%) were also investigated in combination with the Z-907 dye. The overall conversion efficiency of 6.1% at 100 mW cm illumination was reported." ... 

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