Synthesis of magnetic core-shell nanoparticle reagent containing bromide-perbromide and its application as a catalyst for the synthesis of polyhydroquinolines derivatives

Functionalized magnetic core–shell nanoparticles [Fe3O4/SiO2/(CH2)3N+Me3Br3–] are prepared by coprecipitation method, characterized by transmission electron microscopy, FT-IR, X-ray diffraction, and vibrating sample magnetometer. The catalytic activity of these nanoparticles was tested in the syntheses of polyhydroquinoline derivatives in solvent-free conditions. The four-component Hantzsch condensation reaction of dimedone, ethyl acetoacetate, ammonium acetate, and various aromatic and aliphatic aldehydes in the presence of a catalytic amount of magnetic nanoparticle-supported tribromide under solvent‐free conditions affords polyhydroquinoline derivatives in good to excellent yields. The catalyst was readily recovered by use of an external magnet, and was reused repeatedly.