Tetramethyl guanidinium chlorosulfonate as a highly efficient and recyclable organocatalyst for the preparation of bis(indolyl)methane derivatives

•Tetramethylguanidine ionic liquid (TMG IL) is synthesized and characterized.•The TMG IL is an excellent organocatalyst for the synthesis of bisindolylmethanes.•The products are quantitatively obtained at environmentally benign conditions.•The TMG IL catalyst is recyclable without losing its catalytic activity.

The synthesis and characterization of a novel superbase ionic liquid, tetramethylguanidinium chlorosulfonate, are described. The guanidine ionic liquid (GIL) was characterized by FT-IR and NMR spectroscopies, and wide-angle X-ray scattering techniques, as well as thermogravimetric analysis. The GIL functions as an effective, environmentally benign, and recyclable catalyst for the synthesis of various bis(indolyl)methanes in outstanding yields (90–96%), within short reaction times; further, no chromatographic purification step for the product is required.

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