合成路线1

Alkylation of 2-amino-3-nitrophenol (I) with 1,2-dichloroethane in 2-butanone afforded the chloroethyl ether (II), which was further condensed with benzylamine (III) to give amine (IV) (1,2). Acylation of (IV) with trifluoroacetic anhydride provided trifluoroacetamide (V). The nitro group of (V) was then reduced by transfer hydrogenation using hydrazine and Pd/C. Cyclization of the resulting phenylenediamine (VI) in refluxing TFA gave rise to benzimidazole (VII). The trifluoroacetamido group of (VII) was finally removed by treatment with K2CO3 in boiling MeOH (1). In a more direct procedure, nitroaniline (IV) was reduced to diamine (VIII) and then cyclized to the title benzimidazole by treatment with TFA.