SnCl2.2H2O as a green and readily available catalyst for the preparation of 2H-indazolo [1,2-b]-phthalazine-triones under solvent free and microwave irradiation Conditions

Generally, nitrogen containing heterocyclic compounds have a wide range of pharmacological and clinical applications. Among them, phthalazine derivatives have been given considerable attention in recent years because of their wide range of pharmaceutical and biological activities such as antimicrobial, anticonvulsant, antifungal, anticancer, and anti-inflammatory. Moreover, these compounds display good agreement as new luminescent materials or fluorescence probes. In recent years, the development of new methods for the synthesis of heterocyclic rings containing phthalazine is an interesting challenge and therefore a number of procedures have been reported for the synthesis of phthalazine derivatives [1-3]. The first synthesis of indazolo[1,2-b]-phthalazinetriones was reported by Bazgir et al. [4] using p-toluene sulfonic acid (p-TSA) as a catalyst. In this work, an efficient and eco-friendly procedure has been developed for the synthesis of biologically active heterocyclic compounds including 2H-indazolo[1,2-b]-phthalazinetriones in the presence of SnCl2.2H2O as a catalyst through a one-pot three-component condensation reaction of aromatic aldehydes, dimedone, and phthalhydrazide without solvent under microwave irradiation (scheme 1). The present approach provides several advantages such as excellent yields, mild reaction conditions, short reaction times, easy workup compared to the conventional method of syntheses.