Potassium 4,5-diphenylimidazolate, with

Potassium 4,5-diphenylimidazolate with [Cp RuCl] gives the trimer 52 containing the X-T T mode (OOOM5263), which under reflux gives the r -coordi-nated species 53 (R = R = Ph, R = H). The structure of the latter was confirmed by X-ray analysis. In similar conditions 2,4-dimethylimidazole gives species 53 (R = R = Me, R = H) straightforwardly. 

In the presence of potassium cyanide the N-methyl-C-phenylnitrone (112) takes part in yet a further cycloaddition reaction to give l-methyl-4,5-diphenylimidazole. With lithium metal the aldimine (113) forms a delocalized carbanion which will cyclize with aryl cyanides (Scheme 61) (80AHC(27)24l). See also Section 4.08.1.1.3. 

It is a general rule that imidazoles and benzimidazoles are resistant to Friedel-Crafts reactions. This is not surprising since such basic compounds must be markedly deactivated in the presence of Lewis acids. Imidazolin-2-ones appear to be an exception and apparently possess sufficient activation to react. Reactions between imidazoles and Af-methylfor-manilide and phosphoryl chloride are also unproductive. With 4,5-diphenylimidazole, phenyl isocyanate at 80 °C gives products of both N- and C-substitution, but in boiling nitrobenzene only the latter (86) is formed. 2-Methyl-4-phenylimidazole gives (87) under the same conditions, and 1,3-diphenylimidazolium perchlorate is transformed by potassium t-butoxide into a ylide which reacts at C-2 with phenyl isothiocyanate. Sufficient activation is present in l-methyl-2-phenyl-4-phenylaminoimidazole for it to react by substitution at C-5 with acetic anhydride (71JOC3368). 

Reactions of imidazoles with nucleophiles occur slowly as with thiazoles and demand vigorous conditions. Attack of the nucleophile occurs in the 2-position. For instance, l-methyl-4,5-diphenylimidazole reacts with potassium hydroxide at 300°C to give imidazol-2(3//)-one ... 

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