Silica gel-supported tungstic acid (STA): A new, highly efficient and recyclable catalyst for the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione carbonitriles and carboxylates under neat conditions

Abstract

1 H -Pyrazolo[1,2- b ]phthalazine-5,10-dione carbonitriles and carboxylates possess a broad range of applications as active compounds in the pharmacological and biological fields. We developed an efficient and ecofriendly silica gel-supported tungstic acid (STA)-catalyzed one-pot synthesis of 1 H -pyrazolo[1,2- b ]phthalazine-5,10-dione carbonitriles and carboxylates by a three-component reaction of an aldehyde, a malononitrile/ethyl cyanoacetate and a phthalhydrazide under solvent-free conditions. The major advantages of the present method are experimental simplicity, use of an inexpensive and ecofriendly reusable catalyst, good yields, and short reaction times.