Magnetic Fe3O4-supported sulfonic acid-functionalized graphene oxide (Fe3O4@GO-naphthalene-SO3H): a novel and recyclable nanocatalyst for green one-pot synthesis of 5-oxo-dihydropyrano[3,2-c]chromenes and 2-amino-3-cyano-1,4,5,6-tetrahydropyrano[3,2-c]quinolin-5-ones

Abstract

Synthesis of a novel magnetic 1-naphthalenesulfonic acid-grafted graphene oxide (Fe3O4-GO-naphthalene-SO3H) via a three-step procedure has been described. The structure of this newly synthesized nanographene oxide was fully characterized by X-ray diffraction, energy dispersive X‐ray, vibrating sample magnetometer, scanning electron microscopy, Fourier-transform infrared, Raman spectroscopy, and thermo-gravimetric analytical techniques. The catalytic efficiency of these nanoparticles as recyclable nanocatalyst was explored in one-pot three-component reaction between aldehydes, malononitrile, and 4-hydroxyquinolin-2(1H)-one or 4-hydroxycoumarin under green conditions in water for the synthesis of 2-amino-3-cyano-1,4,5,6-tetrahydropyrano[3,2-c]quinolin-5-ones and 5-oxo-dihydropyrano[3,2-c]chromenes (coumarins) respectively. High yields of the products, low reaction times, easy preparation of the catalyst, and use of water as green solvent are the main advantages of this protocol. In addition, the catalyst can be easily separated simply by using a magnet and reused for six fresh runs without significant loss of activity.