Sulfonated Core-Shell Magnetic Nanoparticle (Fe3O4@SiO2@PrSO3H) as a Highly Active and Durable Protonic Acid Catalyst; Synthesis of Coumarin Derivatives through Pechmann Reaction

Sulfonic acid supported silica coated magnetic nanoparticles (Fe3O4@SiO2@PrSO3H), was prepared by using low cost precursors and a facile immobilization technique. The final catalyst, which was characterized by XRD, FT-IR, vibrating sample magnetometer (VSM), TEM, and TGA techniques, was found to be an efficient and environmentally benign solid acid for the Pechmann condensation of substituted phenols with ethyl acetoacetate leading to the formation of coumarin derivatives. After the reaction, the catalyst could be effortlessly separated by external magnet and reused for 22 consecutive runs, without any significant loss in catalytic efficiency. The catalytic system presented offers a reusable strategy for the efficient synthesis of coumarin, simplicity in operation, and a green reaction profile by avoiding toxic conventional catalysts and solvents.