Magnetic Zinc Hydrogen Salt of Phosphotungstic Acid: an Efficient Catalyst for the One-Pot Synthesis of 4H-Pyrans Derivatives.

In this study, a magnetic catalyst of phosphotungstic acid salt (ZnHPMo₁₂O₄₀) was prepared by substitution of protons in H₃PW₁₂O₄₀ with zinc metal cations as a recyclable catalyst. The structural and morphology of the prepared catalysts was investigated using Fourier transform infrared spectroscopy (FT-IR), differential thermal gravimetric analysis (TGA), BET surface analysis emission scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). The prepared catalyst was successfully used as an efficient and recyclable catalyst for the synthesis of 4H-pyrans. The results showed that the magnetic zinc phosphotungstic acid catalyst exhibited good catalytic activity under optimum reaction conditions and the desired products were obtained in good to excellent yields. The good activity of the zinc salt of heteropoly acid catalyst was closely related to its high specific surface area, and the synergistic effects of Lewis and Brønsted acidity. The catalyst stability was good and it can be reused six times without significant loss activity in reaction. [ABSTRACT FROM AUTHOR]