Study of the electrophilic substitution of alkyl-, aryl-, and aralkyl-5(6)-hydroxybenzimidazoles

A series of new 4-sulfo-5(6)-hydroxybenzimidazoles was obtained including mono-, di-, and trinitro derivatives of 2-phenyl- and 2-benzyl-5-hydroxybenzimidazoles. Aromatic groups at C2, in contrast to alkyl groups, enhance the reactivity of the benzimidazole system in electrophilic substitution.