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Paper | Regular issue | Vol 38, No. 11, 1994, pp.2415-2422
Published online, 1st January, 1970
DOI: 10.3987/COM-94-6855
Synthesis of 4-Amino-7-hydroxybenzimidazole

Alan R. Katritzky,* Bogumila Rachwal, Stanislaw Rachwal, Peter J. Steel, and Krzysztof A. Zaklika

*BIOGAL Pharmaceutical Works, H-4042 Debrecen, Hungary


A simple and efficient synthesis of 4-amino-7-hydroxybenzimidazole (2a) was developed involving condensation of 2,3-diaminophenol with triethyl orthoformate, coupling the 4-hydroxybenzimidazole (6) thus obtained with 4-ethylbenzodiazonium chloride to give 4-(4-ethylphenylazo)-7-hydroxybenzimidazole (7) and hydrogenolysis of 7 to give 2a. Acetylation of 2a with acetic anhydride gave triacetyl derivative (8), the structure of which was proved by X-ray crystallographic analysis.