Synergistic Surface Basicity Enhancement Effect for Doping of Transition Metals in Nanocrystalline MgO as Catalysts towards One Pot Wittig Reaction

Abstract The syntheses of Cu, Fe and Mn doped nanocrystalline MgO was carried out using alkali leached hydrothermal technique. The synergistic effect of transition metals (Cu, Fe and Mn) doping, particle size and nano-scale morphology on surface basicity enhancement was established in one pot Wittig reaction. The doped and undoped nanocrystalline MgO catalysts are characterized by XRD, UV-DRS, FT-IR, FESEM, EDS and XPS techniques. XRD study revealed formation of pure cubic phase of undoped and up to 1 wt% Cu, Fe and Mn doped MgO. The FESEM photographs of transition metal doped MgO indicated the formation of prismatic hexagonal nano plates and nanosheets with thickness in the range 20-70 nm. The catalytic activity of synthesized catalysts was investigated in one pot Wittig reaction of benzaldehyde, triphenylphosphine and ethyl bromoacetate at room temperature in DMF solvent. The Mn doped nanocrystalline MgO catalyst shows 98 % yield under optimized reaction conditions. Enhancement of surface basicity due to doping of Mn in MgO was ascertained by UV-DRS and XPS study. The characterization of Wittig product ethyl cinnamate was carried out using HR-MS, 1H-NMR, 13C-NMR. The 1H-NMR evaluates 95:5 % E/Z ratio of ethyl cinnmate. Reported methodology is eco-friendly and easy to scale up.