Cost effective one-pot photocatalytic synthesis of quinaldines from nitroarenes by silver loaded TiO2

In order to get materials with enhanced adsorption and photocatalytic performance, nanosized silver particles loaded TiO2 was prepared by a facile photodeposition. This catalyst was characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller surface area (BET) and diffuse reflectance spectroscopy (DRS). XRD patterns revealed that the crystal structure of Ag–TiO2 resembled anatase phase of TiO2. Visible light absorption increases with the increase in Ag loading. Photoluminescence spectra indicate the suppression of recombination of the photogenerated electron-hole pairs by the loaded silver on TiO2. XPS measurements reveal the presence of silver particles mainly in metallic form. 1.5% Ag loaded TiO2 is found to be most efficient for selective one-pot synthesis of quinaldines from nitroarenes in ethanol using UV light. Ag–TiO2 on irradiation induces a combined redox reaction with nitroarene and alcohol and this is followed by condensation-cyclization of aniline and oxidation products to give quinaldines.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (128 K)Download as PowerPoint slideHighlights► Nano-Ag–TiO2 photocatalyses a combined redox reaction with nitroarene and ethanol. ► Quinaldines have widespread biochemical significance due to their application. ► Our reaction conditions provide selective one pot synthesis of quinaldine. ► Synthesis of quinaldines from nitroarenes are rare in the literature. ► Easy product isolation and mild conditions make this reaction eco-friendly.