BiCl-loaded montmorillonite K10: a new solid acid catalyst for solvent-free synthesis of bis(indolyl)methanes.

We report an efficient green process for synthesis of bis(indolyl)methane derivatives under solvent-free conditions by use of a new solid acid catalyst, BiCl-loaded montmorillonite K10. The catalyst was characterized by SEM, BET surface area measurement, and determination of its surface acidity by temperature-programmed desorption measurements. The salient features of the procedure are its simplicity, ease of preparation of the catalyst, cost effectiveness, excellent yield with short reaction time, reusability of the catalyst, and enhancement of the acidity of montmorillonite K10 catalyst by BiCl loading. Graphical Abstract: Pictogram [Figure not available: see fulltext.]. [ABSTRACT FROM AUTHOR]