2- imidazolium chloride

Given that the p/Ca of imidazolium ion is 7 is a 1 M aqueous solution of imidazolium chloride acidic basic or neutraP What about a 1 M solu tion of imidazole A solution containing equal molar quantities of imidazole and imidazolium chloride ... 

Imid azolin-2-ones polymers, 1, 296 synthesis, 5, 466, 491 Imidazolium cations, 2-fluoro-nucleophilic substitution, 5, 413 Imidazolium chloride, 4-amino-l-methyl-2,3-diphenyl-... 

Dimroth rearrangement, 5, 438 Imidazolium chloride, 4-chloromethyl-reaction with poly(vinyl alcohol), 1, 306 Imidazolium chloride, 2,4,5-tri(diethylamino)-reduction, 5, 415 Imidazolium complexes, 7, 746... 

Tlie desulfurization of thiono compounds is another frequently used synthetic approach for the formation of double bonds via carbenoid intermediates. By this methodology, some indigoid 1,3,5,7-tetraazafulvalenes 88 and 90 were synthesized (83BSB781 90JPR949).Tliis dimerization starting from 2,4,5-tris(dimethylamino)imidazolium chloride via the appropriate thione 87 has been realized in the presence of phosphanes or phosphites to... 

Diels-Alder reactions Neutral ionic liquids have been found to be excellent solvents for the Diels-Alder reaction. The first example of a Diels-Alder reaction in an ionic liquid was the reaction of methyl acrylate with cyclopentadiene in [EtNH3][N03] [40], in which significant rate enhancement was observed. Howarth et al. investigated the role of chiral imidazolium chloride and trifluoroacetate salts (dissolved in dichloromethane) in the Diels-Alder reactions between cyclopentadiene and either crotonaldehyde or methacroline [41]. It should be noted that this paper describes one of the first examples of a chiral cationic ionic liquid being used in synthesis (Scheme 5.1-17). The enantioselectivity was found to be < 5 % in this reaction for both the endo (10 %) and the exo (90 %) isomers. 

FIG. 11 Titration plot of alkanesulfonates. Sample 60 wt % of Hostapur SAS 60, monosulfonates fraction contents ca. 140 mg/100 ml (10% MeOH) solution to be titrated 10 ml, 5 ml buffer pH 3 (Merck), 5 ml MeOH, diluted to 100 ml with water titrant 0.004 mol/l TEGOtrant A 100 (l,3-didecyl-2-methyl-imidazolium chloride, Metrohm 6.2317.000) titrator Titrino 716 DMS with automatic titrator 727 and propellant stirrer titration mode dynamic end point titration (DET), high-sense electrode Metrohm 6.0504.15Q, reference electrode Ag/AgCl Metrohm 6.0733.100, EP = end point. 

Regarding the use of other metals for this transformation, Shirai and co-workers reported that a system constituted by palladium(II) complex [Pd(p-Cl)(r -aUyl)]2 and thioether-imidazolium chloride 19 achieved the arylation of aldehydes with boronic acids [33] and potassium trifluoroborates in good to excellent yields (Scheme 7.5) [34], More recently, Buffard and Itami showed that a NKcod) / IPr-HCl system could catalyse the reaction of arylboronate esters and inactivated aldehydes and ketones (Scheme 7.5) [35]. 

Palladium NHC systems for the hydrodehalogenation of aryl chlorides and bromides and polyhalogenated aromatic substrates originate from about the same time as the first reports on Ni chemistry, and show many similarities. Initial efforts showed that the combination of PdCdba) (2 mol%), one equivalent of imidazolium chloride and KOMe produced an effective system for the reduction of 4-chlorotolu-ene, especially upon use of SIMes HCl 2 (96% yield of toluene after 1 h at 100°C) [7]. Interestingly, higher ligand to metal ratios severely inhibited the catalysis with only 7% yield of toluene achieved in the same time in the presence of two equivalents of SIMes HCl 2. Variation of the metal source (Pd(OAc)2, Pd(CjHjCN)jClj), alkoxide (NaOMe, KO Bu, NaOH/ ec-BuOH) or imidazolium salt (IMes HCl 1, IPr HCl 3, lAd HCl, ICy HCl) all failed to give a more active catalyst. 

An interesting synthesis of a nucleoside carbonic ester was conducted in excellent yield by reaction with 1 -methyl-3 - [2-(p-nitropheny l)ethoxycarbony 1]-imidazolium chloride (for an analogous introduction of the npeoc-protecting group, see also Section 3.10.1) [2393 as mentioned in Section 3.1.8, methylation of the imidazole unit increases significantly the reaction rate. 

The water soluble 1-methyl-3-(methylthiophenyloxycarbonyl)imidazolium chloride is used for introduction of the methylthiophenyloxycarbonyl protecting group at the amino nitrogen of peptides. Higher yields are achieved with this compound than with the corresponding chloroformate. 

Generally, method B is superior to method A, because the imidazolium chloride formed in the reaction can easily be removed by filtration, in contrast to the imidazole formed in method A. 

Acyl chlorides can be prepared by direct acylation of hydrogen chloride with imidazo-lides. If two moles of hydrogen chloride are passed into a solution containing one mole of an imidazolide in a solvent in which the imidazolium chloride is insoluble (e.g., chloroform, dichloroethane), the imidazolium chloride precipitates and the acyl chloride is formed in excellent yield and a high degree of purity. Examples are provided in Table 13-2. ... 

By working quickly, the imidazolium chloride may be removed by suction filtration through a Buchner funnel. However, the precipitate should not be freed of solvent completely because imidazolium chloride is extremely hygroscopic. If the moist precipitate is washed with 50-100 ml. of anhydrous tetrahydrofuran, the yield of 1,1 -carbonyldiimidazole may be slightly increased however, there is some danger of the introduction of too much moisture into the reaction solution. 

Imidazole, purification of, 48, 45 reaction with phosgene, 48, 44 Imldazole, 1,1 -carbonyldi-, 48, 44 Imidazolium chloride, 48, 46 3-Imino-l-( -tolylsulfonyl)pyrazolidine, from 3-amino-3-pyrazoline sulfate and / -toluenesulfonyl chloride, 48, 9... 

Full dissolution has been reported to proceed in ionic liquids such as butyl- or allyl-methyl-imidazolium chloride under microwave irradiation [59, 60], The Clanton is claimed to be essential to favor the de-agglomerization of the cellulose by breaking its H-bonds that hold it together [61]. The cellulose can subsequently be precipitated from the ionic liquid upon addition of, for example, water, without significant depolymerization. 

The synthesis of ionic liquids with BF4 and PF6 as cations has been the subject of much research since they are the most widely used in catalysis. However, it is difficult to make these ionic liquids in a pure form. The original route used to prepare ionic liquids with these anions consists of a metathesis (anion-cation exchange) reaction in which the imidazolium chloride is reacted with the sodium salt of the anion in a suitable solvent [8], The reaction is illustrated in Scheme 4.2 for the tetrafluoroborate salt. 

The results show that basic alkylphosphines are especially suitable. The ligand should be sterically demanding, but tri-f-butylphosphine (entry 8) is obviously too bulky. An ideal ligand seems to be tri-f-propylphosphine (entries 6 and 7). Unfortunately, the water-soluble ligands TPPMS (entries 2 and 3) and TPPTS do not work in this reaction, also the carbene ligand bis(mesitylene)imidazolium chloride (entry 12) has only a low activity. The influence of additives like maleic anhydride (MA) and 1,3-divinyltetra-methyldisiloxane (dvds) is negligible. 

Proton abstraction from the imidazolium chloride (29) by KO Bu gave the carbene (30) originally postulated, but not isolated, by Wanzlick. An X-ray structure determination of the carbene (30) showed the expected near-planarity of the imidazole ring and an NCN angle of 102.1°, characteristic of a singlet carbene. 

Loosely bound fj -cyclopentadienyl anions can also serve as the base to deproto-nate imidazolium salts. When chromocene is reacted with an imidazolium chloride in THF the metal precursor loses one molecule of cyclopentadiene to form the 14-electron complex [( 7 -C5H5)Cr(NHC)Cl] [Eq. (13)]. This complex can be further oxidized by CHCI3 to give [( 7 -C5H5)Cr(NHC)Cl2]. This route also works with nickelocene to generate the corresponding [( -C5H5)Ni(NHC)Cl] complex. ... 

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