A novel and eco-friendly o-phenylendiamine stabilized on silica-coated magnetic nanocatalyst for the synthesis of indenoquinoline derivatives under ultrasonic-assisted solvent-free conditions

In this study, a novel and environmentally benign o-phenylendiamine stabilized on silica-coated Fe3O4 magnetic nanocatalyst (Fe3O4@SiO2@propyltriethoxysilane@o-phenylendiamine-SO3H/HCl) as a hybrid magnetic organometallic nanocatalyst has been synthesized. After that, the structure of this new catalyst was completely characterized via Fourier transforms infrared (FT-IR) spectroscopy, Brunauer–Emmett–Teller (BET), atomic force microscopy (AFM), field-emission scanning electron microscopy (FE-SEM) images, energy dispersive X-ray (EDX) and vibrating sample magnetometer (VSM) analyses. The SEM image of the synthesized nanocatalyst showed that it has a nearly core-shell spherical shape and uniform size distribution with an average size about 40 nm. The BET result revealed that it has 34.88 m²/g specific surface areas. Finally, its catalytic activity was investigated for the selective synthesis of 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one derivatives in high-to-excellent isolated yields under solvent-free conditions and ultrasound irradiation at room temperature. This nanocatalyst can be easily recovered from the reaction mixture using an external magnet and reused for at least eight times without significant decrease in catalytic activity.