Abstract: Benzimidazoles ( 3a 〖WTHZ〗c〖WTBZ 〗, 5〖STBZ〗〖WTHZ〗a 〖WTHZ〗c ) were synthesized in a one step reductive c yclization reaction of o nitroanilines ( 1〖STBZ〗, 4〖STBZ 〗) and aryl aldehydes ( 2〖STBZ〗〖WTHZ〗a 〖WTHZ〗c ). Sodium dithionite was used as a reductive reagent. Selectivity was found when more than one nitro group existed in the substrates. A mixture of ethanol and water was u sed as solvent. The reaction was accelerated by water.

Key words: cyclization, nitro compound, selective reduction , sodium dithionite, benzimidazole