Fe3O4@HNTs-Cellulose-HClO4: New Heterogeneous Catalyst for Smooth and Effective Synthesis of 4H-Pyran and 4H-Chromene Derivatives

This study involved the fabrication of a novel catalyst based on natural clay via straightforward co-precipitation technique. Fe3O4 magnetic nanoparticles and cellulose covalently grafted onto the Halloysite nanotubes (HNTs) after being functionalized with perchloric acid (Fe3O4@HNTs-Cellulose-HClO4). It was characterized by using different analytical techniques to confirm its formation, including Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) pattern, Energy dispersive X-ray (EDAX) analysis, Thermogravimetric analysis (TGA), and Scanning electron microscopy (SEM). This novel heterogeneous catalyst was effectively applied in the synthesis of 4-aryl-4H-pyran-3-carboxylate using an aromatic aldehyde, ethyl acetoacetate and malononitrile and Tetrahydro-4H-chromene using an aromatic aldehyde, dimedone and ethyl cyanoacetate. Gentle reaction parameters, minimal catalyst costs, environmental friendliness, and excellent product yields (97 & 96% respectively) are some of the primary advantages of this approach. The catalyst is easily separated and can be recycled five times without experiencing a noticeable decrease in activity and the hot filtration test demonstrated the catalyst's heterogeneity. With mild reaction conditions and room temperature, easy purification, simple workup, and excellent yields this heterogeneous catalyst demonstrated high efficiency in green media.