V₂O₅/SiO₂ as a Heterogeneous Catalyst in the Synthesis of bis(indolyl)methanes Under Solvent Free Condition

The heterogeneous catalyst of V₂O₅/SiO₂ was prepared and characterized with Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy. XRD of the silicon dioxide used reveals the amorphous nature while the spectrum of the prepared catalyst shows sharp intense peaks at about (20.2, 26.1, 31.0 and 47.3^∘) and less intense sharp peaks at about (51.1, 55.2, 57.1 and 60.4^∘) indicating formation of a crystalline phase with orthorhombic geometry. The FTIR spectra of the catalyst showed characteristic vibration stretching bands of V ∖O at their specified position. An efficient and facile approach for the synthesis of bis(indolyl)methanes through a catalytic one pot reaction. Indole and aromatic aldehydes were stirred in the presence of a catalytic amount of the prepared and characterized heterogeneous catalyst V₂O₅/SiO₂ at 50^∘C under solvent free condition. This procedure has advantages in competition with the previously reported methods, in terms of high yield, green catalyst, mild reaction condition, simple procedure, lack of toxicity, low cost, and simplicity of workup.