Water extract of onion: chemoselective synthesis of 2-substituted benzimidazole derivatives.

A facile, efficient, green synthetic route was developed for the selective synthesis of 2-substituted benzimidazole derivatives via the reaction of 1,2-diamines with aromatic, aliphatic and hetero aromatic nitroalkenes in the presence of an onion extract as a green catalyst. In this reaction, fifteen 2-substituted benzimidazole derivatives were obtained in good to excellent yields (80-95%). The method presented here offers several benefits, including minimal energy usage, cheap, nontoxic catalyst, simple workup procedure and without column purification. The usage of onion extract creates this approach is environmentally friendly and makes a significant addition to the currently available techniques for the creation of 2-substituted benzimidazoles. Further, the scope and constraints were also investigated, and a conceivable reaction mechanism was put forth. [ABSTRACT FROM AUTHOR]