Ag STA: Green and an Efficient Catalyst for Synthesis of Benzimidazole Derivatives at Room Temperature

In the present study, an efficient one-pot, solvent-free protocol has been developed for the synthesis of substituted benzimidazole derivatives at room temperature using silver silicotungstate (Ag-STA) as a recyclable heterogeneous catalyst. The catalyst was prepared according to a reported literature procedure and successfully applied to the cyclocondensation of *o*-phenylenediamines with aromatic aldehydes. Under the optimized conditions, the use of 10 mol% Ag-STA afforded complete conversion of the starting materials and the corresponding benzimidazole products in yields of up to 86%. The catalyst could be recovered and reused for up to six consecutive cycles without a significant loss in catalytic performance or product selectivity. The developed protocol offers several practical advantages, including simple operation, mild reaction conditions, solvent-free processing, straightforward work-up, and catalyst recyclability. These features make the Ag-STA-catalyzed methodology a useful approach for the synthesis of substituted benzimidazole derivatives.

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