Phospho sulfonic acid: A novel and efficient solid acid catalyst for the one-pot preparation of 2H-indazolo[2,1-b]-phthalazine-triones

The efficient one-pot condensation of aldehyde, dimedone, and phthalhydrazide has been achieved in the presence of a catalytic amount of phospho sulfonic acid as a novel environmentally benign heterogeneous solid acid under solvent-free conditions. A diversified 2H-indazolo[1,2-b]phthalazinetrione derivatives were prepared in good to excellent yields in short time. The economical factors (time, cost, waste etc.) for this three-component reaction hold promise for the future of organic synthesis.