The synthetic importance of 2-hydrazinobenzimidazoles
is well known: they underlie the
The main method of the preparation of 2-
hydrazinobenzimidazoles as known is based on the
exchange of a chlorine atom or a sulfo group in the
corresponding benzimidazoles [8]. Hydrazine
derivative I we have obtained in a high yield from 1-
aminobenzimidazole-2-sulfonic acid [9] by boiling in
excess of hydrazine hydrate. This compound proved to
be sufficiently stable and gradually turned darker only
at the long storage.