Reaction of imidazoles with

Two types of imidazolium salts must be distinguished depending on the M.Al -substitution symmetrically (R = R ) and unsymmetricaUy substituted (R R ) versions. For the first type (which is also the predominant one, see Fig. 1.4), two main strategies are viable reaction of imidazole with RX in the presence of a base... 

In what was intended as another experimental probe to ascertain whether a concerted or stepwise mechanism was involved in substitution reactions of arenesulfonyl chlorides, Rogne (1975) measured the enthalpies of transfer from propanol to acetonitrile for the transition states, SAH, for the reaction of imidazole with (a) benzoyl chloride and (b) benzenesulfonyl chloride. He found that SAH was considerably more negative for the reaction involving the sulfonyl chloride than for the one involving benzoyl chloride. This means that the transition state for attack of imidazole on benzenesulfonyl chloride is considerably better solvated by acetonitrile relative to its solvation by propanol... 

Direction of borate structures by specific cations is also illustrated by the formation of the unusual nonaborate anion in the presence of the imidazo-lium, [C3H7N2], and guanidinium, [C(NH2)3], cations [42]. The reaction of imidazole with three molar equivalents of boric acid in aqueous solution results in the spontaneous formation of the imidazolium salt of the [B90i2(OH)6] anion, shown in Fig. 11, associated with three [C3H7N2] ... 

A benzisoxazole moiety provides the nucleus of an anticonvulsant agent whose structure differs markedly from the traditional agents in this class. The synthesis starts with a compound (61-1) that incorporates a preformed benzisoxazole. Bromination proceeds on the position adjacent to the carboxylic acid (61-2). This intermediate loses carbon dioxide on heating, leaving behind the bromomethyl derivative (61-3). Displacement of the halogen with the ion from the reaction of imidazole with sodium hydride yields the alkylation product (61-4). The short side chain is then methylated by successive treatment with a base and methyl idodide to afford zoniclezole (61-5) [64]. 

Fig. 11.6 (A) Spectroscopic detection of acetylimidazole in the imidazole-catalysed hydrolysis of 4-nitro-phenyl acetate at pH 5 (D) and at pH 6 (E) curves are calculated from data in reference [12] and the curve for the acetate ion product (C) is for pH 5. (B) Reaction of imidazole with 4-nitrophenyl acetate (k) and the hydrolysis of acetyl imidazole (k2) curves constructed from data in references [13] and [12].

Table 22.3 ZPE-corrected barrier energies involved at various steps of different mechanisms of reactions of imidazole with HOC1 and N02C1 leading to the formation of 2-oxoIm, 2-chloroIm, and 2-nitroIm obtained at the B3LYP/AUG-cc-pVDZ level of theory in gas phase and aqueous...

V. Gogonea, Potential energy surface of the reaction of imidazole with peroxynitrite density functional theory study. Int. J. Quantum Chem. 104, 342-353 (2005)... 

Reaction of imidazole with chloroformates in the presence of triethyl-amine produces 2-carboxylates (78S675). 

Among the earliest examples for the successful application of the epoxide method is a publication from Glas et al. [169] in which they introduce the reaction of imidazole with cyclohexene oxide, subsequent quartemisation with methyl iodide and the derivatisation of the hydroxyl functional group to an ester (see Figure 3.59). 

The electrostatic attraction contributes to the catalytic efficiency when the solvolysis of negatively charged esters is catalyzed by partially protonated polyvinyl-imidazole (46). For the reaction of imidazole with both NABA and NABS, the catalytic rate constants are linearly dependent upon the fraction of neutral Imidazole... 

Reports of quaternization at the already substituted nitrogen should be viewed with suspicion, and one of the products of the reaction of imidazole with 2,2-dichlorodiethyl sulfide (mustard gas) designated as (55) is more likely to be (56) or (57). The observations of Pinner and Schwarz in 1902 that the quaternary salt obtained from 1-methylimidazole and 1-bromopentane could be decomposed by alkali to give both aminomethane and 1-aminopentane was the first piece of evidence (more recently confirmed by NMR studies) to support the accepted view that quaternization takes place at the unsubstituted ring nitrogen. 

Alkaline medium, however, is not always suitable since branched-chain alkyl halides are subject to elimination, and there are striking changes in orientation of substitution with unsymmetrically substituted imidazoles. Only low yields of l-(l-imidazolyl)-2-methyl-propane are obtained in the reaction of imidazole with l-iodo-2-methylpropane in sodium-liquid ammonia. 

Reactions of imidazoles with dienophiles such as DMAD usually lead not to normal Diels-Alder adducts, but to products of (V-alkylation (Scheme 68 see also Section 4.07.1.3.11) (78AHC(23)265, 79JCS(P1)1239). 

Fig. 1 shows the change in the yield of N-Ml with time on stream in the reaction of imidazole with methanol over H-forms of various zeolites. A 100% yield of N-MI was maintained for 5 h over H-Y. The stable activities were observed for H-Beta and H-ZSM-5, while deactivation was observed for H-mordenite and H-L. 

The effect of the reaction temperature on the yield of N-Ml in the reaction of imidazole with methanol over H-Y is shown in Fig. 2. The yield of the methylation product was 48% at 493 K, increased with reaction temperature and reached 100% at 553 K. 

The reactions of imidazole with alcohols other than methanol over H-Y were also examined and the results are summarized in Table 2. 

The yields of 1-methylimidazole by the reaction of imidazole with methanol... 

In the above set of acetate esters shown in Fig. 10, the rate equation for the reaction of imidazole with esters contains a term first-order in imidazole (either a nucleophilic or general base reaction), a term second-order in imidazole, and a term first-order in imidazole and first-order in hydroxide. The general rate expression is given in equation (26). 

In the case of unsymmetrical reactions the equilibrium constant can be calculated for any donor provided it is known for any one donor. The equilibrium constant (Aeq = 0,37) for the reaction of imidazole with 4-nitrophenyl acetate (Equation 14, Ar = 4-nitrophenyl = 4NP) can easily be measured by use of forward and reverse rate constants (Agq = The equilibrium constant for the reaction is governed by a Bronsted Equation logA q = + C where P is the value As, the... 

An interesting mechanistic application of free energy relationships in calculating rate constants concerns the reactivity of the putative intermediate in the reaction of imidazole with 4-nitrophenyl acetate. The putative stepwise process (Scheme 15) involves a zwitterionic tetrahedral intermediate which would decompose to the product A-acetylimidazole, subsequently hydrolysing to acetate ion and imidazole. 

Scheme 15 Equilibria in the reaction of imidazole with 4-nitrophenyl acetate the equilibrium data are from ref 28...

From the p values of 1-(3-aminopropyl)- and l-(2-aminoethyl)-imidazoles the linear free energy relationship exists between the free energy change for the replacement of an hydroxyl group in a carbonyl hydrate by imidazolyl, and the sum of the a values for other substituents. The implications of these results are that a concerted rather than a stepwise mechanism is likely for the reactions of imidazole with aryl acetate <87CJC1951>. 

Analysis of isomeric product ratios from reactions of imidazoles with perfluoroalkyl halides has been achieved by use of F NMR <84JOC1060,90TL1279). 

Jursic, B. S., Zdravkovski, Z., Reaction of Imidazoles with Ethylene and Singlet Oxygen An Ab Initio Theoretical Study, J. Org. Chem. 1995, 60, 2865 2869. 

Fig. 11 Volume profile for the reaction of imidazole with tra i,-[Co(en)2(Me)H20]2+ in aqueous solution at 10 °C.

Preparation of 5-amino-6-oxo-l,6-dihydro-1,2,4-triazine-3-carboxylic acid derivatives and the synthesis of compound libraries thereof have been reported <04TL2791>. Intramolecular inverse electron demand Diels-Alder reactions of imidazoles with 1,2,4-triazines have been described as a new route to obtain l,2,3,4-tetrahydro-l,5-naphthyridines and related heterocycles... 

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