A Bronsted acidic ionic liquid anchored to magnetite nanoparticles as a novel recoverable heterogeneous catalyst for the Biginelli reaction

In this study, simple and effective methods were used for the preparation of an ionic liquid that immobilized magnetite nanoparticles. Fe3O4 nanoparticles were prepared via a chemical co-precipitation method. Then, a SiO2 shell was coated on the magnetic core via the Stober method. Finally, CPTES (chloropropyltriethoxysilane) and morpholine were coated on the SiO2 shell. Morpholine sulfate, an acidic ionic liquid, was successfully bound to magnetite nanoparticles (Mag@Morph-AIL) and this was used as an efficient catalyst for the preparation of 3,4-dihydropyrimidinones. Compared to previous works, the easy separation of the nanocatalyst using an external magnet and the recyclability, non-toxicity, versatility, and high stability of the catalyst, combined with low reaction times and excellent yields, make the present protocol very useful for the synthesis of the title products. The synthesized products and catalyst were confirmed via(1)H-NMR, C-13-NMR, FT-IR, scanning electron microscope, X-ray diffraction, and elemental analysis.

Automated summary

This study utilized a chemical co-precipitation method to prepare Fe3O4 nanoparticles, followed by coating a SiO2 shell using the Stober method, and finally coating CPTES and morpholine on the SiO2 shell to successfully synthesize Mag@Morph-AIL. The nanocatalyst showed easy separation, recyclability, non-toxicity, versatility, high stability, short reaction times, and excellent yields, making it a useful method for the preparation of 3,4-dihydropyrimidinones.