OICC Press Iranian Journal of Catalysis 2345-4865 3 4 2024 02 03 Melamine trisulfonic acid (MTSA) as an efficient catalyst for the synthesis of triazolo[1,2-a]indazole-triones and some 2H-indazolo[2,1-b]phthalazine-triones EN Ardeshir Khazaei Faculty of Chemistry, University of Bu-Ali Sina, 65178, Hamedan, Iran. Mohammad Ali Zolfigol Department of Organic Chemistry, Faculty of Chemistry, Bu-Ali Sina University, Hamedan 6517838683, Iran. Toktam Faal Rastegar Faculty of Chemistry, University of Bu-Ali Sina, 65178, Hamedan, Iran. Gholamabbas Chehardoli School of Pharmacy, University of Medical Sciences, Hamedan 65178, Iran. Shadpour Mallakpour Nanotechnology and Advanced Materials Institute, Isfahan University of Technology, Isfahan, Iran. Journal Article 2024 02 03 Melamine trisulfonic acid (MTSA) as an efficient heterogeneous catalyst has been used for the one-pot preparation of triazolo[1,2-a]indazole-1,3,8-trione and 2H-indazolo[2,1-b]phthalazine-1,6,11-trione derivatives by the three-component condensation reaction of urazoles or phthalhydrazide, dimedone or 1,3-cyclohexanedione, and aldehydes under solvent-free conditions in good to excellent yields and short reaction times.