Reusable (MWCNTs)-COOH/Fe3O4-CaO Magnetic Nanostructure Promoted Three-Component Synthesis of Hexahydroacridine Derivatives

(MWCNTs)-COOH/Fe3O4-CaO magnetic nanostructure was employed for the high-yield synthesis of hexahydroacridine-1,8-dione derivatives via three-component reaction of dimedone, unprotected sugars, and aniline or 4-bromoaniline in ethanol under reflux conditions.  (MWCNTs)-COOH/Fe3O4-CaO was prepared by COOH functionalized multi-walled carbon nanotubes (MWCNTs)-COOH with Fe3O4-CaO nanoparticles in the presence of FeSO4 and eggshell. This heterogeneous hybrid nanostructure, (MWCNTs)-COOH/Fe3O4-CaO, was determined by SEM, TEM, XRD, EDX, FT-IR, and TGA. The potential application of this covalently linked basic catalyst was also investigated as an efficient, recyclable, and heterogeneous catalyst for the synthesis of hexahydroacridine-1,8-dione. The condensation of dimedone with unprotected sugars and aniline or 4-bromoaniline in the presence of a catalytic amount of (MWCNTs)-COOH/Fe3O4-CaO magnetic nanostructure gave hexahydroacridine-1,8-dione derivatives in good yields. The products were identified by FT-IR, NMR spectra, and elemental analysis. The catalyst was separated by an external magnet from the reaction mixture, washed, and dried at 100 °C for 2 h. The recovered catalyst was then re-entered into a fresh reaction mixture and recycled 5 times without considerable loss of activity.