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Tungstic acid-functionalized polycalix[4]resorcinarene as a cavity-containing hyper-branched supramolecular and recoverable acidic catalyst in 4H-pyran synthesis†
Aref Mahmoudi Asl,Bahador Karami,Zahra Karimi
RSC Advances Pub Date : 05/02/2023 00:00:00 , DOI:10.1039/D3RA00804E
Abstract

In this study, tungstic acid immobilized on polycalix[4]resorcinarene, PC4RA@SiPr–OWO3H, as a mesoporous acidic solid catalyst was synthesized and investigated for its catalytic activity. Polycalix[4]resorcinarene was prepared via a reaction between formaldehyde and calix[4]resorcinarene, and then the resulting polycalix[4]resorcinarene was modified using (3-chloropropyl)trimethoxysilane (CPTMS) to obtain polycalix[4]resorcinarene@(CH2)3Cl that was finally functionalized with tungstic acid. The designed acidic catalyst was characterized by various methods including FT-IR spectroscopy, energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), elemental mapping analysis and transmission electron microscopy (TEM). The catalyst efficiency was evaluated via the preparation of 4H-pyran derivatives using dimethyl/diethyl acetylenedicarboxylate, malononitrile, and beta-carbonyl compounds, confirmed by FT-IR spectroscopy and 1H and 13C NMR spectroscopy. The synthetic catalyst was introduced as a suitable catalyst with high recycling power in 4H-pyran synthesis.

Graphical abstract: Tungstic acid-functionalized polycalix[4]resorcinarene as a cavity-containing hyper-branched supramolecular and recoverable acidic catalyst in 4H-pyran synthesis
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