Nanostructured N doped TiO2efficient stable catalyst for Kabachnik-Fields reaction under microwave irradiation

Herein, we report nitrogen-doped TiO2(N-TiO2) solid-acid nanocatalysts with heterogeneous structure employed for the solvent-free synthesis of alpha-aminophosphonates through Kabachnik-Fields reaction. N-TiO(2)were synthesized by direct amination using triethylamine as a source of nitrogen at low temperature and optimized by varying the volume ratios of TiCl4, methanol, water, and triethylamine, under identical conditions. An X-ray diffraction (XRD) study showed the formation of a rutile phase and the crystalline size is 10 nm. The nanostructural features of N-TiO(2)were examined by HR-TEM analysis, which showed they had rod-like morphology with a diameter of similar to 7 to 10 nm. Diffuse reflectance spectra show the extended absorbance in the visible region with a narrowing in the band gap of 2.85 eV, and the high resolution XPS spectrum of the N 1s region confirmed successful doping of N in the TiO(2)lattice. More significantly, we found that as-synthesized N-TiO(2)showed significantly higher catalytic activity than commercially available TiO(2)for the synthesis of a novel series of alpha-amino phosphonatesviaKabachnik-Fields reaction under microwave irradiation conditions. The improved catalytic activity is due to the presence of strong and Bronsted acid sites on a porous nanorod surface. This work signifies N-TiO(2)is an efficient stable catalyst for the synthesis of alpha-aminophosphonate derivatives.