A New Versatile Protocol for the Synthesis of Indazolophthalazinetriones

Potassium hydrogen sulfate (KHSO 4 ) and trifluoromethanesulfonic acid (CF 3 SO 3 H) 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 CF 3 SO 3 H is a stronger acid than KHSO 4 , and the corresponding intermediate will probably be formed at a higher rate and be more stable.