A New Versatile Protocol for the Synthesis ofIndazolophthalazinetriones

Potassium hydrogen sulfate (KHSO4) and trifluoromethanesulfonic acid (CF3SO3H) were separately used as efficient catalysts for the one-pot three-component synthesis of a series of indazolophthalazinetriones from various aldehydes, dimedone, and 2,3-dihydrophthalazine-1,4-dione at 80°C under solvent-free conditions in good to excellent yields. It was found that trifluoromethanesulfonic acid is a more efficient catalyst than potassium hydrogen sulfate since CF3SO3H is a stronger acid than KHSO4, and the corresponding intermediate will probably be formed at a higher rate and be more stable.