A new green protocol has been developed for the synthesis of 2H-indazolo [2, 1-b] phthalazine-triones via one-pot, three-component condensation reaction of aromatic aldehydes with 1, 3-dicarbonyl compounds and phthalhydrazide using reusable dodecylphosphonic acid (DPA) as heterogeneous solid acid catalyst under solvent-free conditions. This protocol provides a novel and improved method for obtaining 2H-indazolo ...