Room temperature synthesis of 2-benzimidazoles with hydrogen peroxide as oxidant and supported ammonium molybdate as catalyst

摘要

An environmentally benign method with hydrogen peroxide as oxidant has been developed for the synthesis of 2-benzimidazoles from aromatic aldehydes and o-phenylenediamine. Ammonium molybdate catalyzes this transformation, and supported ammonium molybdate was more active than the unsupported compound. Results from characterization imply SiO2-supported ammonium molybdate has a planar structure, which explains its high activity but poor stability, because of loss of active species during the reaction. Good activity and stability were observed for TiO2 and gamma-Al2O3-supported ammonium molybdate; this was ascribed to the porous structure of the supports and the highly dispersed active species.