Novel acidic ionic liquid [BEMIM][HSO4]: A highly efficient and recyclable catalyst for the synthesis of bis-indolyl methane derivatives

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The novel acidic ionic liquid [BEMIM][HSO4] was prepared and characterized by FT-IR, 1H NMR, 13C NMR, DEPT-135, LC-Mass, and elemental analysis techniques. It was examined as a catalyst for the synthesis of bis-indolyl methane derivatives at ambient temperature, and an important advantage was that it required only short reaction times. The crude bis-indolyl methane products could be purified by a simple recrystallization process, avoiding time-consuming chromatography. The catalyst was reusable, and even after five runs, an insignificant loss in the activity of the catalyst was observed. The chemical integrity of the recovered catalyst after the fifth run was confirmed by FT-IR, 1H NMR, and Mass analysis. This reaction has a high value of the environmental factor (E).