Owing to their good stability, high surface area and easy synthesis, magnetic nanoparticles (MNP) have recently been applied as heterogeneous catalytic supports [1]. An attractive feature of MNP-supported catalysts is that they can be easily separated with the aid of an external magnet, thus facilitating easy catalyst recycling without using extra organic solvents and additional filtration steps. 2H-Indazolo[2,1-b]phthalazine-triones are a class of heterocycles that attracted much attention because they have been reported to possess a wide range of pharmaceutical and biological activitie [2]. The typical procedure for the synthesis of phthalazines fused with indazole involves three-component condensation of phthalhydrazide, aromatic aldehydes, and cyclic 1,3-diones compounds using acids as a catalyst under various conditions [3], on the basis of our knowledge, there isn't any report on application of base catalyst for the synthesis of 2H-indazolo[2,1-b]phthalazine-triones. The advantages of MNP-supported catalysts prompted us to investigate synthesis of novel MNP-supported catalyst and its application in organic synthesis. MNP-supported guanidine was synthesized according to the procedure. The catalyst has been characterized by scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FT-IR). A SEM image of MNPs-guanidine is shown in Figure 1A, it was confirmed that the catalyst was made up of nanometer-sized particles. The IR spectrum of MNPs-PSA shows peaks that are characteristic of a functionalized guanidine group. The MNP-supported guanidine was next used as magnetically heterogeneous nanocatalyst for the synthesis of 2H-indazolo[2,1-b]phthalazine-trione derivatives from one-pot, three-component condensation of phthalhydrazide, different aromatic aldehydes, and cyclic 1,3-diones compounds under solvent-free conditions at 100°C In summary, the nanocatalyst is easily synthesized and can catalyze synthesis of 2H-indazolo[2,1-b]phthalazine-tri
