An approach to the synthesis and characterization of HMS/Pr-Rh-Zr as efficient catalyst for synthesis of tetrahydrobenzo[b]pyran and 1,4-dihydropyrano[2,3-c]pyrazole derivatives

Abstract

The aim of present investigation is the synthesis of mesoporous catalyst based on hexagonal mesoporous silica. HMS support has exceptional properties such as easy synthesis, high surface area, large pore volume and wormhole pores. These distinctive characteristics beseem use of it as a support for synthesis of heterogeneous catalyst. With functionalization of HMS and immobilization of Zr-rhodanine complex into functionalized HMS, HMS/Pr-Rh-Zr was obtained. New synthesized catalyst (HMS/Pr-Rh-Zr) characterized by FT-IR, XRD, TGA, SEM, EDX, adsorption–desorption of nitrogen at 77 K and ICP techniques. These techniques confirmed that the heterogeneous catalyst of HMS/Pr-Rh-Zr was successfully synthesized. Also the catalytic activity of HMS/Pr-Rh-Zr is investigated for the synthesis of tetrahydrobenzo[b]pyran derivatives from reaction between aldehyde, malononitrile, dimedone in PEG at 80 °C and synthesis of 1,4-dihydropyrano[2,3-c]pyrazole derivatives from reaction between aldehyde, ethyl acetoacetate, malononitrile and hydrazine hydrate in H2O:EtOH at 35 °C. These results confirmed the HMS/Pr-Rh-Zr exhibited good catalytic performance. Furthermore, the synthesized heterogeneous catalyst could be recovered after the reaction and reused several times without any noticeable loss in activity. Also zirconium leaching of HMS/Pr-Rh-Zr was studied whereupon metal leaching of the catalyst was very low.