Fe3O4 magnetic nanoparticles in the layers of montmorillonite as a valuable heterogeneous nanocatalyst for the one-pot synthesis of indeno[1,2-b]indolone derivatives in aqueous media

In the present work, iron oxide nanoparticles (Fe3O4-NPs) were prepared using a chemical coprecipitation method. At room temperature, Fe3O4-NPs are put in interlamellar space and external surfaces of montmorillonite (MMT) as a supported solid. The MMT@Fe3O4 was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA) and Fourier transform infrared spectrophotometry (FT-IR). Then, indeno[1,2-b]indolone derivatives were catalyzed by magnetic MMT@Fe3O4-NPs. MMT@Fe3O4-NPs were found to be a recoverable organocatalyst for the effective synthesis of the indeno[1,2-b]indolone derivatives via one-pot multicomponent cyclocondensation of ninhydrin, 1,3-diketo compound and amine derivatives in water. The significant advantages of this method are excellent yield, mild conditions, eco-friendly catalyst, low expense, and not using an environmentally harmful catalyst or solvent.