An efficient and practical synthesis of bis(indolyl)methanes catalyzed by N-sulfonic acid poly(4-vinylpyridinium) chloride

•Introduction of an efficient solid acid for the synthesis of bis(indolyl)methane derivatives.•Application of solvent-free conditions, use of grinding stone method and minimization of the amount of organic solvent used.•No side reactions, ease of preparation and handling of the catalyst, facilitate the separation of the product from the catalyst.•High yields, short reaction times, effective and reusability catalyst.

A mild, simple and convenient procedure for the synthesis of bis(indolyl)methane derivatives was described using N-sulfonic acid poly(4-vinylpyridinium) chloride as an efficient, cheap, and reusable catalyst under mild conditions.

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