Hydrochloric acid immobilized on nano‐titanium dioxide: a novel and efficient nanocatalyst for the synthesis of tetrahydrobenzo[b]pyrans

Abstract

Hydrochloric acid was immobilized onto the surface of amine functionalized nano‐titania. For this purpose, 2,4‐toluene diisocyanate (TDI) as a bi‐functional covalent linker was grafted onto a nano‐titania and next, the unreacted isocyanate groups were then reduced with water and finally, the prepared amine group in the previous step was reacted with hydrochloric acid in order to producing ammonium chloride salt. This efficient nanocatalyst was evaluated in the synthesis of tetrahydrobenzo[b]pyrans, which affords high yields (67-93%) and short reaction time (15-30 min). The synthesized nanocatalyst was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, thermogravimetric analysis, and Mohr method titration.

Keywords

• supported hydrochloric acid
• 2
• 4‐toluene diisocyanate
• heterogeneous nanocatalyst
• tetrahydrobenzo[b]pyrans