Benzoyl-4-phenylimidazole

Benzoyl chloride (2.4 g, 17 mmol) is slowly added to a stirred solution of 4-phenylimidazole (2.0g, 14mmol) and sodium hydroxide (1.2g, 28mmol) in acetone (10 ml) and water (40 ml). During the addition the product precipitates. After 30 min cold water (50 ml) is added to ensure complete precipitation. The solid is filtered, washed with water, dried and recrystallized as white platelets from chloroform-ether (3.3 g, 95%), m.p. 124.0 124.5°C. 

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Less common as a synthetic method is the rearrangement under mild conditions of some hydrazinium salts. In contrast to the severe conditions necessary (200 C, solid KOH) to rearrange 1,1,1-trialkylhydrazinium salts [60], 1,1-dimethyl-l-phenacylhydrazinium bromide is transformed merely by refluxing in pentanol or pyridine into 2-benzoyl-4-phenylimidazole (65-73%). This is a Stevens-type rearrangement [61, 62]. 

Quatemization is sometimes difficult to avoid but can be used positively. Quatemization can provide entry into 5-substituted A-alkylated imidazoles. For example, A-ethylation of iV-benzoyl-4-phenylimidazole with a powerful alkylating agent like triethyloxonium tetrafluoroborate provides the salt that undergoes hydrolysis under mildly basic conditions to provide 5-phenyl-iV-ethylimidazole. ... 

A 25% yield of 2-phenylimidazole has been obtained136 by the action of ammonium carbonate in ethanol on l-benzoyl-2-cyanoaziri-dine (29) [from the reaction of a-chloro-j0-benzoylaminopropionitrile (30) with liquid ammonia]. Imidazolium salts have been isolated from... 

Imidazole reacts very slowly with singlet oxygen to form the imida-zolidone (86)42S through an elimination reaction involving proton loss and cleavage of the oxygen-oxygen bond of the transannular peroxide (87). On the other hand, 4-phenylimidazole forms a hydantoin derivative (88) and V-benzoyl-V -methoxycarbonylurea (89). This... 

In the remarkable formation of 2-benzoyl-6-nitrobenzimidazole (40) on irradiation of l-(2,4-dinitrophenyl)-4-phenylimidazole (35), either a dipolar cycloaddition or a radical process could lead to the proposed ort/jo-nitrosoimine intermediates (36, 37). Certainly the ortho-niito group could take part in a 1,3-cycloaddition at C-2 and C-5, and subsequent rupture of the 1,2- or 1,5-bonds could lead to these intermediates. Recyclization would give rise to (38) and (39) after hydrolysis and deoxygenation the former would form (40), while (39) would be expected to produce a 2-aminobenzimidazole product (Scheme 11) (76BSF192). 

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 remarkable formation of 2-benzoyl-6-nitrobenzimidazole by irradiation of l-(2,4-dinitrophenyl)-4-phenylimidazole has been reported. " Either a dipolar cycloaddition or a radical process could account for the formation... 

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