A novel class of heterogeneous catalysts based on toluene diisocyanate: the first amine-functionalized nano-titanium dioxide as a mild and highly recyclable solid nanocatalyst for the Biginelli reaction

Abstract

Amine-functionalized titania as a novel inorganic-organic hybrid heterogeneous basic nanocatalyst has been synthesized by the covalent grafting of toluene diisocyanate as a precursor of amine on the surface of titania. The prepared nanocatalyst was characterized by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, X-ray diffraction and thermogravimetric analysis. The catalytic activity of resultant nanocatalyst was effectively evaluated for the synthesis of 3,4-dihydopyrimidin-2(1H)-ones through a one-pot three components condensation reaction of various aldehydes, b-dicarbonyl compounds and urea (or thiourea) at 100°C under solvent-free conditions with good to excellent yields. Optimization of the reaction condition was investigated by central composite design under response surface methodology. The catalyst can be recovered easily by simple filtration and reused for eight consecutive runs without significant decrease of its catalytic efficiency.

Nickel(II) Schiff base complex supported on nano‐titanium dioxide: A novel straightforward route for preparation of supported Schiff base complexes applying 2,4‐toluenediisocyanate

“…In continuation of our current programmes for the procurement of novel heterogeneous catalysts for organic reactions by applying TDI, we report the synthesis and application of Ni(II)–Schiff base complex supported on nano‐TiO 2 (nano‐TiO 2 ‐SA‐Ni(II)) as a novel, efficient and recyclable nanocatalyst. For the first time, TDI was employed as a precursor of amine groups for preparation of the Schiff base ligand.…”

“…In continuation of our efforts towards expanding the application of 2,4‐toluenediisocyanate (TDI) in heterogeneous catalyst synthesis, in the work reported in this paper, for the first time, we successfully synthesized a novel nickel(II) Schiff base complex, applying TDI as a covalently bound linker and precursor of amine groups immobilized on nano‐titania support. TDI is highly accessible, of low cost and very active due to its reactive unsaturated bonds and was used as a bridge between the surface of nano‐titania and nickel(II) ion to improve the recyclability and life span of the inorganic–organic hybrid catalyst.…”

Sulfamic Acid‐functionalized Nano‐titanium dioxide as a Novel and Highly Efficient Heterogeneous Nanocatalyst for One‐pot and Solvent‐free Synthesis of Hexahydroquinolines

“…In this paper, in continuation of our studies on applying green catalysts for organic transformations, we investigate the catalytic activity of nano (n)‐TiO 2 ‐NHSO 3 H for the synthesis of hexahydroquinolines (Scheme ).…”

Deep eutectic solvent‐assisted synthesis of highly efficient nanocatalyst (n‐TiO2@TDI@DES (ZnCl2:urea)) for chemoselective oxidation of sulfides to sulfoxides

“…For further evaluation of the environmentally friendly chemical procedures, [83][84][85] the synthesized TiO 2 @-TDI@DES was employed as an interphase catalyst in the chemoselective oxidation of various structures of sulfides to their corresponding sulfoxides at solvent-free condition using 30% H 2 O 2 at ambient temperature. Initial tests were conducted to optimize the reaction condition in which the methyl phenyl sulfide oxidation was considered as a model and the impacts of time, product yield, oxidant, and catalyst were explored (Table 2).…”