Benzyl Alcohol → (4-Amino-3-nitrophenyl)methanol

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Reaction Steps

The required keto benzimidazole reactants in which R4 is hydrogen can be prepared from 4-chloro-3-nitrobenzyl alcohol. The benzyl alcohol is ammoniated to give 4-amino-3-nitrobenzyl alcohol which is hydrogenated catalytically to yield 4-hydroxymethyl-o-phenylenediamine. The phenylenediamine is reacted with cyanogen bromide by the methods known to the benzimidazole art to provide 2-amino-5(6)-hydroxymethylbenzimidazole. The hydroxymethyl group of the benzimidazole compound can be oxidized with Jones reagent (a solution of chromic acid and sulfuric acid in water) to provide the corresponding 5(6)-formyl benzimidazole.

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