One-Pot Synthesis of New Highly Functionalized Pyridine-Fused Pyrazolo[1,2-b]phthalazine Derivatives

Pyrazole and phthalazine moieties receive special attention in the pharmaceutical and medical industries as essential ingredients in certain drugs. It is known that these substances exhibit a wide range of biological functions. A new method has been developed for the synthesis of pyridinefused pyrazolo[1,2-b]phthalazine derivatives via a three-component reaction of phthalhydrazide, aromatic aldehydes, and 2-aminopropene-1,1,3-tricarbonitrile. This transformation presumably occurs via Knoevenagel condensation, Michael addition, cyclization and isomerization sequence of reactions. Noteworthy features of this protocol include easy isolation, a broad substrate range, noncolumn chromatographic separation and high product yields. Benzaldehydes containing electronwithdrawing groups, such as Br, Cl, F, CN and NO2, were found to be very reactive in the process and to provide good yields of the appropriate pyridine-fused pyrazolo[1,2-b]phthalazine derivatives. In addition, the electron-donating groups such as hydroxyl, methoxy, ethoxy and isopropyl were also favourable for the transformation. In conclusion, the current study describes a straightforward new one-pot, three-component method for the synthesis of pyridine-fused pyrazolo[1,2-b]phthalazine derivatives. The transformation requires the use of an inexpensive and readily available catalyst and does not require column chromatographic purification for isolation of products. The devised protocol's primary advantages are its straightforward experimental process, wide range of substrates, and high yields.