A robust three-step procedure for the preparation of 1,2-disubstituted benzimidazole derivatives has been developed via oxidative cyclization as the key step to give four new compounds 6a-d in good yield (79-85%). Sodium metabisulfite, Na₂S₂O₅ was found to be the most effective oxidant compared to others for the success of the benzimidazole ring closing steps. Moreover, in the case of 6a, the one-spot two-step synthesis was found to be better than the separated ones in term of both yield and ease of purification. The mechanism of the synthetic process was deducted for 1,2-disubstituted benzimidazoles formation. Bioassays have been conducting for these new
1,2-disubstituted benzimidazoles.