Reusable silica supported poly phosphoric acid catalyzed three-component synthesis of 2H-indazolo[2,1-b]phthalazine-trione derivatives

An efficient synthesis of 2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-trione derivatives from the three-component condensation reaction of phthalhydrazide, dimedone, and aromatic aldehydes under solvent-free conditions in good to excellent yields and short reaction times using reusable silica supported poly phosphoric acid (PPA-SiO2) as heterogeneous acid catalyst has been investigated.