Brønsted acidic ionic liquid ([BMIm]HSO4) as an efficient catalysts for the one-pot synthesis of 2H-indazolo[2,1-b]phthalazine-trione derivatives

The Brønsted acidic ionic liquid ([BMIm]HSO4) catalyzed three-component synthesis of 2H-indazolo[2,1-b]phthalazine-trione derivatives at room temperature. The integrity of the ionic liquid remains reasonably unchanged when it is separated from the reaction mixture by water extraction, as it can be recycled several times without any loss of activity in each of the title syntheses. The products and ionic liquid could be conveniently separated from the reaction mixture, indicating that the whole process was performed as a green chemical transformation. The salient features of this one pot protocol are short reaction times, cleaner reaction profiles and simple workup.