Fe3O4@SiO2@(CH2)3-urea-quinoline sulfonic acid chloride: A novel catalyst for the synthesis of coumarin containing 1,4 dihydropyridines

Abstract

Fe3O4@SiO2@(CH2)3-urea-quinoline sulfonic acid chloride, as a novel and efficient nanomagnetic catalyst bearing urea linkers, was designed, synthesized and then fully characterized by using various techniques. To investigate the catalytic activity of the described catalyst, it was used for the synthesis of coumarin containing 1,4-dihydropyridines (DHPs), through a condensation reaction of aromatic aldehydes, 4-hydroxycoumarin, and ammonium acetate under solvent-free conditions. This procedure includes important aspects like simple procedure, simplicity of product isolation using water, decreasing the temperature of reaction, disuse of solvent, high to excellent yields, environmentally benign reaction conditions and short reaction times. Also, the presented catalyst was recycled and reused for at least five times with only a negligible decrease in its catalytic activity. The applied catalyst has both acidic and H-bond donor-acceptor sites so that it can use as a dual role catalytic system.