Fe3O4@SiO2@TDI@DES: A novel magnetically separable catalyst for the synthesis of oxindoles

A novel magnetically separable Fe3O4@SiO2@TDI@DES catalyst was synthesized by covalent anchoring of Deep Eutectic Solvent [DES; oxalic acid: choline chloride] on Fe3O4@SiO2@TDI magnetic nanoparticles. The structure of the catalyst was confirmed by FT-IR, XRD, EDX, TGA-DTA, VSM, FE-SEM, and HR-TEM analyses. The syn-thesized magnetically separable catalyst demonstrated excellent catalytic activity in the terms of yield and re-action time for the synthesis of 2,2 -(2-oxoindoline-3-3diyl)bis(1H-indene-1,3(2H)-dione) from 1,3-indendione and isatin. In addition, the catalyst could be reused for five runs without significant loss of catalytic activity. The synthesized oxindole derivatives showed promising in vitro antioxidant activities which were further supported by molecular docking and molecular dynamic (MD) simulation studies.