Durable magnetite-chitosan core-shell nanoparticles as reusable green nanocatalyst for the benign one-pot three-component synthesis of spirooxindoles and spirochromenes at ambient temperature under both solvent-free and ultrasonic conditions in aqueous ethanol solution

In the present research, a novel, efficient, and green nanocatalyst has been afforded by coating Fe3O4 nanoparticles with chitosan through simple and readily available chemicals. Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, dynamic light scattering, vibrating sample magnetometer, and thermogravimetric analyses were used to describe this nanocatalyst. The catalytic performance of the Fe3O4@chitosan heterogeneous nanocatalyst was investigated in an environmentally benign and efficacious fabrication of a variety of spirooxindole and spirochromene derivatives in high yields via employing three-component reactions of malononitrile, dimedone, and isatin in a solvent-free medium (Method A) and under ultrasonic conditions in EtOH/H2O (Method B) at ambient temperature. The achieved nanocatalyst could be easily removed from the mixture of the reaction and was recyclable seven times via a simple external magnet without appreciable loss in catalytic proficiency. Several other advantages of this methodology were environmental friendliness, simple operation, excellent yields, economical handling, and easy workup.