Novel Redox Photocatalyst Pt-TiO2 for the Synthesis of 2-Methylquinolines from Nitroarenes

An eco-friendly and efficient procedure for synthesis of 2-methylquinoline derivatives from nitroarenes has been developed by a simple one-pot reaction on the surface of platinum-loaded TiO2 with neat ethanol under UV irradiation without any harsh reagent according to green chemistry. TiO2 catalysts with various amounts of Pt loadings were prepared by photodeposition using chloroplatinic acid solution and characterized by XRD, BET, AFM, HR-TEM, XPS, and DRS. XRD patterns showed that the crystal structure of Pt-TiO2 still remained as anatase phase. The UV-vis spectra indicated that Pt promoted the absorption of visible light. The XPS measurements reveal that platinum particles are present mainly in metallic form. AFM and HR-TEM analysis revealed the presence of nonspherical shaped platinum nanoparticles of the diameter 3-12 nm. Pt-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 2-methylquinolines.