Green Synthesis of Dihydropyrimido[4,5‐b]quinolinetriones by Sulfonic Acid‐Functionalized Silica‐Coated CoFe <sub>2</sub> O <sub>4</sub> as a Solid Acid Nanocatalyst under Thermal and Ultrasonic Conditions
Pegah Mahdipour, Leila Moradi, Mahdi Mirzaie
Abstract
Abstract Sulfonic acid functionalized silica coated cobalt ferrite nanoparticles (CoFe 2 O 4 /SiO 2 −SO 3 H) was prepared as an efficient solid acid catalyst for the green synthesis of dihydropyrimido[4,5‐b]quinolinetrione derivatives. CoFe 2 O 4 NPs were prepared by co‐precipitation method and then the silica‐coated CoFe 2 O 4 NPs were modified with chlorosulfonic acid. Obtained CoFe 2 O 4 /SiO 2 −SO 3 H was characterized by thermo gravimetric analysis (TGA), Fourier transform‐infrared spectroscopy (FT‐IR), scanning electron microscope (SEM), energy‐dispersive X‐ray spectroscopy (EDX), X‐ray diffraction (XRD) and vibrating‐sample magnetometer (VSM). The magnetically separable CoFe 2 O 4 /SiO 2 −SO 3 H was successfully used for the four component reaction of barbituric acid, dimedone, amines (or ammonium acetate) and benzaldehyde derivatives for the synthesis of dihydropyrimido[4,5‐b]quinolinetriones under thermal and ultrasound conditions. The advantages of presented simple protocol are the easily separation of magnetic catalyst from the reaction medium by an external magnet, short reaction times, green reaction conditions in addition to simple workup and high yield of products.