Efficient Synthesis of Bis(indolyl)methane Compounds in the Presence of Recyclable Nickel Oxide/Alumina Nanocatalyst

Bis(indolyl)methane derivatives, known for anticancer, antimicrobial, and antioxidant properties, have garnered significant research interest. This study reports an efficient and environmentally friendly method for synthesizing bis(indolyl)methanes via a one-pot reaction between indole and aromatic aldehydes using a nickel oxide/alumina nanocatalyst. The catalyst was prepared by co-precipitation of nickel nitrate hexahydrate and urea in the presence of γ-Al₂O₃, followed by calcination, and characterized using TEM and SEM techniques to confirm its nanoscale morphology. The reactions were performed in water as a solvent under reflux conditions, giving high product yields (up to 97%) within short reaction times (15 min). All the catalyst is inferior of the known CeO₂ catalyst, it allows the use of water instead of chloroform as a solvent. The catalyst was successfully recycled up to five times without significant loss in efficiency, demonstrating its stability and reusability. Experimental methods included monitoring the reaction progress using thin-layer chromatography and product characterization by IR and NMR spectroscopy. The proposed method for the synthesis of bis(indolyl)methane derivatives offers advantages such as simple product separation, low catalyst consumption, and minimal purification losses, presenting a sustainable and effective approach for the synthesis of bis(indolyl)methanes.