OICC Press Iranian Journal of Catalysis 2345-4865 8 3 2024 02 03 Synthesis, characterization and catalytic application of Fe3O4@Cys–SO3H for preparation of 2H-indazolo[1,2-b]phthalazine-triones EN Somaye Nikzad Shalkouhi Department of Chemistry, Rasht Branch, Islamic Azad University, Rasht, Iran. Hassan Kefayati Department of Chemistry, Rasht Branch, Islamic Azad University, Rasht, Iran. 0000-0002-0818-054X Shahab Shariati Department of Chemistry, Rasht Branch, Islamic Azad University, Rasht, Iran. Journal Article 2024 02 03 The surface ofFe3O4 magnetic nanoparticles (MNPs) was modified by L-cysteine through condensation of COOH groups of L-cysteine and OH groups on the surface of Fe3O4. The –SH group of preparedFe3O4@Cys MNPs oxidized to –SO3H group and Fe3O4@Cys–SO3H as an environmentally friendly magnetic nanoparticle was prepared. The MNPs were characterized by FT-IR, XRD, SEM and TEM studies. Then, the catalytic activity of the MNPs was evaluated as an effective and reusable catalyst for one-pot synthesis of 2H‐indazolo [1,2‐b] phthalazine‐triones derivatives. The results show that the catalytic activity of Fe3O4@Cys–SO3H was comparable to that of other reported heterogeneous and homogeneous catalysts.