Thiourea dioxide‐grafted γ‐Fe2O3/HAp magnetic nanoparticles: Efficient,green and reusable nanocatalyst for synthesis of pyranopyridine derivatives

A novel t hiourea dioxide‐functionalized hydroxyapatite‐encapsulated hybrid core‐shell γ‐Fe₂O₃@HAp‐TUD nanoparticles (MNPs) were prepared and characterized by FT‐IR, EDX, SEM, XRD, TGA and VSM analytical methods. The catalytic activity of these MNPs was evaluated through one‐pot three‐component reactions between various substituted aldehydes, malononitrile and 3‐cyano‐6‐hydroxy‐4‐methyl‐pyridin‐2(1H )‐one to afford the corresponding pyrano2,3‐b]pyridines in high yields under mild and solvent‐free conditions. The catalyst can be easily recycled in a magnetic field and reused in five consecutive runs without significant decrease of its catalytic activity.