Fe₃O₄ magnetic nanoparticles coated with a copolymer: a novel reusable catalyst for one-pot three-component synthesis of 2-amino-4H-chromene

Abstract

In this paper, an efficient method for the synthesis of 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromene derivatives is described. The method uses Fe₃O₄ magnetic nanoparticles coated with poly (ε-caprolactone)/poly (ethylene glycol)/poly (ε-caprolactone) (MNPs-Fe₃O₄/PCL–PEG–PCL) as a biodegradable and green catalyst under solvent-free conditions. The catalyst was prepared from PCL–PEG–PCL copolymer and MNPs-Fe₃O₄ and characterized by FT-IR, X-ray diffraction and SEM spectroscopy. Most aromatic aldehydes bearing electron-withdrawing or electron donating groups reacted successfully with malononitrile and dimedone under solvent-free conditions at 80 °C. The corresponding chromenes were isolated in good to excellent yields and the structures of them were confirmed by ¹H NMR and IR spectroscopy. The catalyst could be recovered using an external magnet without a considerable loss in its catalytic activity. Moreover, some advantages of this method are simplicity of procedure, easy separation of the catalyst, high yields, efficiency, stability and non-toxicity of the catalyst, short reaction times, and environmentally benign conditions.