[Bu3NH] [HSO4] catalyzed: an eco-efficient synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones and 2H-indazolo[2,1-b]phthalazine-triones under solvent-free conditions

A Bronsted acidic ionic liquid [Bu3NH][HSO4] as an eco-efficient catalyst for the one-pot multicomponent synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones and 2H-indazolo[2,1-b]phthalazine-triones by using various aldehyde, malononitrile/dimedone, and phthalhydrazide in the absence of a solvent at 80 degrees C is described. Further, the catalyst is prepared from readily available reagents and fully characterized by different techniques such as FT-IR, H-1-NMR, C-13-NMR, and TG, DTG and DTA analyses. The current synthetic protocol offers the mild reaction conditions, short reaction times (9-30 min), excellent yields of the products (83-95%), a clean and straightforward work-up, reusability of the catalyst up to seven catalytic runs, and a sustainable alternative to the existing methods.