Novel type of SO₃H–functionalized nano‐titanium dioxide as a highly efficient and recyclable heterogeneous nanocatalyst for the synthesis of tetrahydrobenzo[b]pyrans

Abstract

n-Butylsulfonated nano-titania (n-TiO 2 -NH-(CH 2 ) 4 -SO 3 H) as a highly efficient and reusable nanocatalyst was prepared by grafting 2,4-toluene diisocyanate as a bi-functional covalent linker onto a nano-titania support, followed by reduction and then ring opening-reaction of the synthesized amine with 1,4-butanesultone. Fourier transform infrared spectroscopy, X-ray diffraction, field-emission scanning electron microscopy and thermogravimetric analysis were used to characterize the catalyst. The catalytic activity of n-TiO 2 -NH-(CH 2 ) 4 -SO 3 H was evaluated in the synthesis of tetrahydrobenzo[b]pyrans, which affords high yields. Statistical experimental design was applied as an efficient and powerful method to achieve the optimal conditions for this catalytic reaction leading to high yield. Moreover, the catalyst was recovered and reused at least six times without a significant decrease in catalytic activity.

SO3H‐functionalized nano‐MGO‐D‐NH2: Synthesis, characterization and application for one‐pot synthesis of pyrano[2,3‐d]pyrimidinone and tetrahydrobenzo[b]pyran derivatives in aqueous media

“…Two significant peaks at 1037 and 1213 cm −1 confirm the reaction of MGO‐D‐NH 2 with 1,4‐butanesultone that correspond to the symmetric and asymmetric stretching vibrations of S═O, respectively (Figure d). The effective functionalization of 1,4‐butanesultone onto the surface of MGO‐D‐NH 2 is evidenced by the FT‐IR results …”

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, [27][28][29][30][31][32][33][34]37] 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.…”

“…[25] Furthermore, being inexpensive, readily available, having high atom efficiency and generating water as the only by-product are advantageous properties of hydrogen peroxide over other oxidants. [26] In continuation of our efforts towards expanding the application of 2,4-toluenediisocyanate (TDI) in heterogeneous catalyst synthesis, [27][28][29][30][31][32][33][34] 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.…”

A novel nanomagnetic solid acid catalyst for the synthesis of new functionalized bis‐coumarin derivatives under microwave irradiations in green conditions

“…Moreover, surface modification of magnetic nanoparticles is an allowable method to eliminate the giant gap between homogeneous and heterogeneous catalysts 63–67 . Sulfuric acid is used as an efficient and irretrievable Brønsted–Lowry acid catalyst to generate different kinds of chemical materials 68–71 . Sulfonation with sulfosalicylic acid as a suitable, quick, and executable system has attracted great attention for the production of heterogeneous catalysts 72 .…”