Synthesis of 2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-triones using 1,4-disulfo-1,4-diazabicyclo[2.2.2]octane-1,4-diium dihydrogen sulfate {DABCO(HSO3)2(HSO4)2} as a new ionic liquid catalyst

• A new acidic ionic liquid catalyst for the preparation of the 2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-triones is prepared.
• The prepared catalyst is nonmetallic and safe.
• The prepared catalyst is reusable and eco-friendly catalyst.
• The reactions are performed at low temperature in high yields.
• The method is easy and contains simple experimental procedure.

1,4-Disulfo-1,4-diazabicyclo[2.2.2]octane-1,4-diium dihydrogen sulfate {DABCO(HSO3)2(HSO4)2} as a new ionic liquid, is prepared and characterized by using different methods including FT-IR, NMR, Mass and SEM analysis as well as determination of the Hammett acidity function. This reagent can be used as an efficient catalyst for the promotion of the synthesis of 2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-trione derivatives as important biologically active compounds with pharmaceutical properties. All reactions are performed in the absence of solvent using small amounts of the catalyst. Easy preparation of the catalyst, simple and easy work-up, mild reaction conditions, green process, excellent yields and short reaction times are the most important advantages this of method.

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