Efficient one-pot syntheses of 2H-indazolo[2,1-b] phthalazine-triones by catalytic H2SO4 in water–ethanol or ionic liquid

Sulfuric acid-catalyzed, three-component, one-pot condensation of phthalhydrazide, aromatic aldehydes and 1,3-dicarbonyl compounds has been reported for the synthesis of a series of 2H-indazolo[2,1-b] phthalazine-triones in water–ethanol or in ionic liquid. The protocol proves to be efficient and environmentally benign in terms of high yields, low reaction times, ease of recovery, and reusability of reaction medium (ionic liquid).