Preparation, characterization, and catalytic application of metallic nanocrystalline MgAl2O4 in the synthesis of 3-hydroxy-3-indolyl-indolin-2-ones, symmetrical and unsymmetrical 3,3′-bis(indolyl)indolin-2-ones, and 3,3′-bis(indolyl)methanes

Nanocrystalline MgAl2O4 has been synthesized via co-precipitation method and characterized by Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. The synthesized nanocatalyst has been utilized for the one-pot condensation of indoles and isatins to prepare 3-hydroxy-3-indolyl-indolin-2-ones and symmetrical and unsymmetrical 3,3'-bis(indolyl)-indolin-2-ones. The one-pot pseudo three-component condensation of indoles and various aldehydes has also been examined to afford 3,3'-bis(indolyl)methanes. Short reaction times, reusability and recovery of the nanocatalyst, in addition to solvent-free reaction media are some advantages of this eco-friendly procedure. (C) 2019 Published by Elsevier B.V. on behalf of King Saud University.