Benzylimidazole

Oxidative-addition of iodine also was investigated for the complex C -bzimAu]3. This complex behaves like most of the CTCs since it adds iodine at only one gold center to yield [p,-N, C -bzimAu]3l2 [59]. The X-ray structure shows that it consists of discrete trinuclear units with the three gold atoms bridged by 1 -benzylimidazolates. 

The hydrochloride salt of 4-amino-1-benzylimidazole (83 R = H) was acetylated readily by acetic anhydride to give the acetamide derivative (83 R = COCHj) (55%) (74JMC1168). Treatment with acetic-formic anhydride gave the corresponding formamide (83 R = CHO). 

The trinuclear derivatives [Au3(p-MeC6H4N = OEt)3] and [Au3(Bzim)3] (Bzim = 1-benzylimidazolate) are colorless complexes but can produce brightly colored materials by sandwiching Ag+ or Tl+ ions and forming linear-chain complexes (Figure 1.35) with interesting luminescence properties such as thermochromism [224]. They also... 

Methyl and methylene groups attached to an imidazole nitrogen can be metallated. In 1-benzylimidazole the extent of benzylic metallation increases with temperature and with the amount of butyllithium used. Although 1-phenylthio-methylbenzimidazole is initially lithiated at C(2) at low temperatures, when the temperature is raised, rearrangement to the rather unstable methylene-lithiated species occurs, but this anion can be trapped by electrophiles. 

Benzophenone reacts differently with 1,2-dimethylimidazole. While acetone gives (153), the diarylketone adds at the 2-methyl group, and with 1-benzylimidazole reaction is at the exocyclic methylene (Scheme 73) <80AHC(27)241,80JHC1777). 

While removal of an AT-alkyl substituent is not always a feasible process benzyl groups can be removed by reduction with sodamide or by catalytic hydrogenolysis. If such reductive methods fail, an oxidation with chromium trioxide in acid may be successful. Other groups are not so readily displaced, but a procedure involving transalkylation with benzyl chloride followed by debenzylation can be employed to convert 1-methylimidazole into imidazole (Scheme 137). The reaction is capable of extension and operates because the quaternary salt is in equilibrium with both 1-alkylimidazoles and the alkyl halides. Under conditions in which the more volatile alkyl halide can escape from the system the 1-benzylimidazole builds up. 

Methyl and methylene groups attached to nitrogen are not normally regarded as reactive , but some metalation experiments using 1-benzylimidazole as substrate indicate reaction at the exocyclic methylene b-76MI4070i). 

Benzyl-5-chloroimidazole cannot be readily made by benzylation of 4(5)-chloroimidazole the other isomer (1,4) is the major product. Nor is chlorination of 1-benzylimidazole a feasible alternative. (See (Chapters 7 and 8.)... 

A mixmre of aqueous formaldehyde (d 1.08, 25 ml) and 1-benzylimidazole (15.8 g, 0.1 mol) is heated in a sealed glass tube at 150°C (3 h). After cooling, the mixture is treated with water (200 ml) and extracted with dichloromcthane (3 X 30 ml). The organic extracts are washed with water (2 x 50 ml), dried... 

To a solution of 1-methylimidazole (5g, 61 mmol) in acetonitrile (60 ml) is added sequentially benzoyl chloride (7.1 ml, 8.6 g, 61 mmol) and triethylamine (8.5 ml, 6.2 g, 61 mmol). After 15h at 25°C the triethylamine hydrochloride is filtered off, the acetonitrile is rotary evaporated, and the residue is boiled (30 min) with aqueous sodium carbonate. Continuous extraction with chloroform of the alkaline solution yields, after removal of the dried solvent, an oil which is distilled to give a pale yellowish liquid (4.2 g, 37%), bi 149°C. Similarly prepared are ethyl l-methylimidazole-2-carboxylate (bo.os 60°C), 2-bcnzoyl-l-phenylimidazole (61%, b2 210°C) and 2-benzoyl-1-benzylimidazole (68%, m.p. 66°C). 

The mass spectrum of I-methyl-4-nitroimidazole-5-carboxylic acid amide shows the elimination of water by an electron impact as distinct from the usual thermal process. In l,4,5-trimethylimidazole-2-carboxylic acid the principal loss is that of CO2. Subsequent loss of O, OH, and HCN was also observed (Schofield et al., p. 173). Ferguson and Schofield (pp. 172,173) have reported considerable data for imidazole JV-oxides. Thus 1-methoxy-4,5-dimethyl-2-phenylimidazole (which loses OCH3 and CH3CN from the fragment m/e 171) is readily distinguished from l,4,5-trimethyl-2-phenyl-imidazole 3-oxide (loss of O and OH). The spectra of 1-benzylimidazoles are dominated by the tropylium ion. ... 

The mass spectra of 1-benzylimidazoles are dominated by the tropylium (CiWi ) ion. 

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