The cyclization of 3,4-diaminobenzophenone (I) with acetylimidic acid ethyl ester (II) in refluxing methanol gives 5-benzoyl-2-methylbenzimidazole (III), which is reduced with NaBH4 in methanol yielding 5-(alpha-hydroxybenzyl)-2-methylbenzimidazole (IV). Finally, this compound is condensed with imidazole (V) in refluxing acetonitrile.
Liarozole fumarate is prepared as shown in Scheme 20970301a. Anisol is reacted with 3-chlorobenzoyl chloride (I) under Friedel-Craft conditions to give (3-chlorophenyl)(4-methoxyphenyl)methanone (II). Nitration of (II) is carried out in dichloromethane at 10 C to yield (III). The methoxy group in (III) is replaced by the amino group by means of NH3 in 2-propanol at 100 C under pressure, giving (IV). By reduction of the keto function of (IV) with sodium borohydride in 2-propanol, the corresponding alcohol (V) is obtained, which upon treatment with 1,1'-carbonyldiimidazole in refluxing dichloromethane yields the imidazolyl compound (VI). Hydrogenation of the nitro group in (VI), followed by cyclization of (VII) in a refluxing mixture of formic acid and 4N hydrochloric acid, gives the benzimidazole derivative (VIII). Finally, the treatment of (VIII) with fumaric acid in ethanol yields liarozole fumarate (IX).