Solvent-free, sonochemical, one-pot, four-component synthesis of 2H-indazolo[2,1-b]phthalazine-triones and 1H-pyrazolo[1,2-b]phthalazine-diones catalyzed by Fe3O4@SiO2-imid-PMAn magnetic nanoparticles

A practical and green method for the synthesis of 2H-indazolo[2,1- b]phthalazine-triones and 1H-pyrazolo[1,2-b]phthalazine-diones using Fe3O4@- SiO2-imid-PMAn nanoparticles as an eco-friendly magnetic catalyst from the fourcomponent condensation, solvent-free reaction of phthalic anhydride, hydrazinium hydroxide, 1,3-diketones, and aldehydes under thermal or ultrasound irradiation at room temperature is described. This new procedure has notable advantages such as operational simplicity, excellent yields, short reaction time, and absence of any tedious work-up or purification. In addition, thermal stability, easy preparation and separation of the catalyst make it a good heterogeneous system and a useful alternative to other heterogeneous catalysts. Also, the catalyst can be easily recovered by a magnetic field and reused for eight consecutive reaction cycles without significant loss of activity.

Multi-component synthesis  2H-Indazolo[2,1-b]phthalazine-triones  1H-Pyrazolo[1,2-b]phthalazine-diones  Solvent-free conditions  Ultrasound irradiation  Heterogeneous magnetic catalyst