Imidazolium acetyl

Imidazolium halides pyrolysis, 5, 449 Imidazolium ions acylation, 5, 402 H NMR, 5, 352 hydrogen exchange, 5, 417 nucleophilic attack, 5, 375 reactivity, 5, 375 ring opening, S, 375 Imidazolium oxides in pyrrole synthesis, 4, 344 Imidazolium perchlorate, 1,3-diphenyl-acylation, 5, 402 Imidazolium salts 1-acetyl-... 

Alleti, R., W.S. Oh, M. Perambuduru, Z. Afrasiabi, E. Sinn and V.P. Reddy, Gadolinium Triflate Immobilized in Imidazolium Based Ionic Liquids A Recyclable Catalyst and Green Solvent for Acetylation of Alcohols and Amines, Green Chemistry, 7, 203-206 (2005). 

The coordination of amido functionalised carbene ligands, where the amido function is introduced by the acetylation of an amino functionalised imidazolium salt, to transition metals has already been discussed in Section 3.1. Here it suffices to mention that the synthesis is similar to other carbonyl functionalised NHC ligands and their transition metal complexes. A suitable example is given in Rivera and Crabtree [226]. 

A totally different approach to bis-carbene ligands on a cyclic scaffold comes from Burgess and coworkers [351], They start from AA -dimethyl-l,2-diaminocyclohexane and acetylate this compound with chloroacetic acid chloride. Addition of an N-substituted imidazole yields the chiral bis-imidazolium salt (see Figure 3.110). Reaction with silver(I) oxide and carbene transfer to palladium(II) completes the reaction sequence. 

Studies of the variation of enzymic activity with pH have indicated that a-amino and imidazolium groups are important entities in the potato phosphorylase molecule, and this evidence has been further substantiated by the results of photo-oxidation and acetylation experiments. Rabbit-muscle phosphorylase a has been modified by photo-oxidation and alkylation, and the effect of both procedures was markedly decreased by the presence of D-glucosyl phosphate or glycogen this result indicates that the amino acid residues affected are at, or near, the active center. These acids may be histidine and cysteine, but other interpretations of the results are possible. 

Studies of crystal structure have been made for imidazole the results from a low-temperature study are illustrated in Fig. 1. In 4,5-di-t-butylimidazole the ring dimensions are essentially similar, although the 4,5-bond is slightly stretched. Among derivatives of imidazole which have been examined are histidine hydrochloride, 4-acetylamino-2-bromo-5-isopropyl-l-methylimidazole, 4-acetyl-5-methyl-2-phenylimid-azole, imidazole-4-acetic acid hydrochloride, imidazole imidazolium... 

N-Acylimidazoles (azolides) have continued to provide a synthetic source of acid derivatives,and the various olysis reactions of these compounds have been studied. " The reactions of acetyl-imidazolium ions with amines have been found to depend largely on amine basic) The thermal decarboxylation of JV-alkoxycarbonylimid-... 

The reaction of acylimidazoles with imidazole is subject to both imidazole and imidazolium ion catalysis (Fife, 1965). The latter reaction is no doubt due to the imidazole-catalyzed hydration of acetylimidazolium ion, as in 18, and fully analogous to the N-methylimidazole-catalyzed hydrolysis of N-acetyl,N -methylimidazolium ion. The mechanism of the former reaction is undefined at the present time, since no 0 exchange studies have been performed with acylimidazoles in more alkaline solution where imidazole catalysis occurs. The leaving group, the imidazole anion, is quite basic (piC = 14-5) therefore it is possible that general base-catalyzed decomposition of the neutral tetrahedral intermediate (24) or general acid-assisted decomposition of the anionic tetrahedral intermediate (25) may occur. The general base-catalyzed alkaline hydrolysis of amides most probably occurs by the... 

A broader exploitation of cellulose solubility in ionic liquids lies in modification of cellulose into more useful forms. Cellulose acetate is currently the most useful derivative of cellulose, with uses in photographic film, as a synthetic fibre and as a component of adhesives. Acetylation of cellulose has been carried out effectively in l-allyl-3-methylimidazolium chloride [Amim][Cl], [C4mim CI], [C2mim][Cl], l-butyl-2,3-dimethylimidazolium chloride [C4dmim][Cl] and l-allyl-2,3-dimethyl-imidazolium bromide [Admim][Br] [136, 159-162], The first report of cellulose acetylation in an ionic liquid involved a one-step reaction in [Amim][Cl] without catalyst, yielding cellulose acetate with a controllable degree of substitution [136], Yields of cellulose acetate of up to 86% have been obtained via reaction in [C4mim] [Cl] at 80 °C for 2 h [160],... 

The lipase-catalysed enantioselective acylation of allylic alcohols in an ionic liquid solvent was demonstrated by Itoh et al. [16] (Fig. 7.7). They found that the acylation rate was strongly dependent on the counter anion of the imidazolium salt, while the lipase-catalysed acylation proceeded with high enantioseleclivity in all ionic liquid tested. Good results were obtained when the reaction was carried out in [bmimT [PFg ] or [bmun" ][BF ]. Other examples of kinetic resolution of allylic alcohols catalysed by lipases in ionic liquids were also reported by these authors [71, 72]. The transesterification of 5-phenyl-l-penten-3-ol under reduced pressure at 27 hPa and 40°C was carried out using methyl phenylthioacetate as acyl donor in [bmim+] [PF ] and [bdmim ][BF ], for obtaining the corresponding acylated compound in optically pure form [71], The acetylation of methyl mandelate catalysed by immobilised P5L in [bdmim ][BF ] is another example reported by these authors about the successful application of ionic liquids as reaction media in racemic resolutions... 

Imidazoles.—Formation. Several new syntheses of imidazoles from isocyanides have been reported these include the formation of 1-alkyl-imidazoles (396) by the action of primary amines on 2-isocyano-2-tosylstyrene, PhCH=C-(NOTos, the cyclization of the enamine Me2NCH=C(NC)C02Me to compound (397) in the presence of methyl iodide,and the preparation of the ethers or thioethers (398) from isocyano-cyanides R CH(NC)CN by their reaction with alcohols or thiols R XH, respectively.Aromatic aldehydes are converted into 2-aryl-4,5-dichloroimidazoles (399) by the combined action of cyanogen and hydrochloric acid. 5-Acetyl-4-methylimidazole (400) results when form-amido-acetylacetone, AC2CHNHCHO, is heated with formamide and formic acid. Exhaustive chlorination of tetramethyldithio-oxamide leads to the tri-chloro-imidazolium cation (401). ... 

The synthesis of l-pyridylimidazol[l,5-a]pyridines from the condensation reaction of 1,2-dipyridylketone, 2-benzoyl and 2-acetyl pyridines, aromatic aldehydes, and ammonium acetate is shown in Scheme 3b. A small selection of imidazolium PILs and AILs were trialed as solvents and catalysts, and for a specific reaction under the same conditions, the PILs led to yields of 69—93%, compared to those... 

DMAP = N,N-dimethylaminopyiidine, DMF = N -dimethylformamide, DCM = dichloromethane, PTAT = phenyltrimethylammonium tribromide, EO = ethylene oxide, PO = propylene oxide, ECH = epichlrohydrin, SO = styreneoxide, AGH = allylicglycidil ether. BO = butylene oxide, HO = n-hexene oxide, DO = N-decene oxide, PPO = 2-phenylpropylene oxide, PS-DFILX = polymer supported diol functionalized ionic liquids, acac = acetyl acetonate, CIL= carboxylic-acid functionalized imidazolium-based ILs, note active site consideration for TOP calculation is not uniform. Co-valent triazine complexes... 

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