Novel silica tungstic acid (STA): Preparation, characterization and its first catalytic application in synthesis of new benzimidazoles

A novel silica tungstic acid (STA) as a highly efficient catalyst has been synthesized and employed for the cyclocondensation of 1,2-phenylenediamines with orthoesters under solvent-free conditions. Catalyst loadings can be as low as 1 mol% to give high yields of the corresponding benzimidazoles at 80 °C. To make the catalyst, sodium tungstate reacted with silica chloride under refluxing n-hexane. The STA as a novel solid acid was characterized by X-ray fluorescence, X-ray diffraction, and Fourier transform infrared spectroscopy.

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► New silica tungstic acid (STA) was prepared through the simple experimental procedure.
► Silica tungstic acid was characterizaed by XRD, XRF and FT-IR spectroscopy.
► Silica tungstic acid was used as a green solid acid catalyst.
► Silica tungstic acid is recyclable and also exhibited very high activity.