Unexpected reduction of C-Cl bond to C-H bond by hydrazine-mediated reaction during the synthesis of alkylbenzimidazoles derivatives

Abstract EN

Acid-catalyzed cyclocondensation of 2-chloroacetic acid and 2-chloropropionic acid with some substituted o-phenylenediamines afforded the corresponding 2-(1-chloroalkyl) benzimidazoles.

Upon treatment with hydrazine hydrate, in order to obtain hydrazine-containing compounds as suitable precursors for construction of new heterocyclic systems, the latter compounds underwent an overall unexpected reduction of the C-Cl bond to C-H bond in a sequence of SN2 followed by bonds (atom) rearrangment to furnish 2-alkylbenzimidazoles.