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One-pot green synthesis of propargylamines using ZnCl2 loaded TiO2 nanomaterial under solvent-free conditions has been effectively accomplished. The aromatic aldehydes, amines, and phenylacetylene were reacted at 100 °C in the presence of the resultant catalyst to form propargylamines. The nanocrystalline TiO2 was initially synthesized by a sol–gel method from titanium(IV) isopropoxide (TTIP) and further subjected to ZnCl2 loading by a wet impregnation method. X-ray diffraction (XRD) patterns revealed the formation of crystalline anatase phase TiO2. Field emission scanning electron microscopy (FESEM) showed the formation of agglomerated spheroid shaped particles having a size in the range of 25–45 nm. Transmission electron microscopy (TEM) validates cubical faceted and nanospheroid-like morphological features with clear faceted edges for the pure TiO2 sample. Surface loading of ZnCl2 on spheroid TiO2 nanoparticles is evident in the case of the ZnCl2 loaded TiO2 sample. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Ti4+ and Zn2+ species in the ZnCl2 loaded TiO2 catalyst. Energy-dispersive X-ray (EDS) spectroscopy also confirmed the existence of Ti, O, Zn and Cl elements in the nanostructured catalyst. 15% ZnCl2 loaded TiO2 afforded the highest 97% yield for 3-(1-morpholino-3-phenylprop-2-ynyl)phenol, 2-(1-morpholino-3-phenylprop-2-ynyl)phenol and 4-(1,3-diphenylprop-2-ynyl)morpholine under solvent-free and aerobic conditions. The proposed nanostructure-based heterogeneous catalytic reaction protocol is sustainable, environment-friendly and offers economic viability in terms of recyclability of the catalyst.

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.

Synthesis of 4,4'-((phenyl)methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) derivatives was successively carried out using Cu doped ZnO nanomaterials. The nanocrystalline Cu-ZnO was obtained by decomposing as-synthesized copper-zinc oxalate intermediate at 520 °C. The prepared Cu-ZnO nanostructured catalyst was characterized with FTIR, X-ray diffraction, field emission scanning electron microscope and electron diffraction techniques. XRD analysis indicates the formation of highly crystalline hexagonal phase of ZnO along with the presence of monoclinic CuO. FESEM photographs shows the existence of plate like structures made up of small spherical shaped particles having size in the range of 30-50 nm. As-synthesized Cu-ZnO was used as heterogeneous catalyst for one pot synthesis of 4,4'-((phenyl)methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) derivatives using phenyl hydrazine, ethyl acetoacetate and aromatic aldehydes. The 3-methyl-1-phenyl-1H-pyrazol-5-ol was obtained as in-situ precursor to the series of bis-pyrazolone derivatives. The progress of reaction was monitored by thin layer chromatography. The obtained organic product was further characterized and confirmed by FT-IR, 1H-NMR, 13C-NMR and HRMS spectroscopic techniques. The Cu-ZnO catalyst confers upto 96% yield of pyrazolone derivatives in ethanol solvent at refluxing condition. The Cu-ZnO catalyst was used successfully up to 5 cycles without much loss of catalytic activity. Overall, the use of environmental friendly Cu-ZnO nano-structures as a heterogeneous catalyst shows higher yield and lower reaction time towards the synthesis of bispyrazolone derivatives by Tandem Knoevenagel/Michael reaction.