ZnCl 2 loaded TiO 2 nanomaterial: an efficient green catalyst to one-pot solvent-free synthesis of propargylamines.

One-pot green synthesis of propargylamines using ZnCl 2 loaded TiO 2 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 TiO 2 was initially synthesized by a sol-gel method from titanium(iv) isopropoxide (TTIP) and further subjected to ZnCl 2 loading by a wet impregnation method. X-ray diffraction (XRD) patterns revealed the formation of crystalline anatase phase TiO 2 . 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 TiO 2 sample. Surface loading of ZnCl 2 on spheroid TiO 2 nanoparticles is evident in the case of the ZnCl 2 loaded TiO 2 sample. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Ti 4+ and Zn 2+ species in the ZnCl 2 loaded TiO 2 catalyst. Energy-dispersive X-ray (EDS) spectroscopy also confirmed the existence of Ti, O, Zn and Cl elements in the nanostructured catalyst. 15% ZnCl 2 loaded TiO 2 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.