Synthesis of New Pyrimido[4′,5′:3,4]pyrazolo[1,2‐b]phthalazine‐4,7,12‐triones: Derivatives of a New Heterocyclic Ring System

Abstract

Several derivatives of the new pyrimido[4′,5′:3,4]pyrazolo[1,2‐b]phthalazine‐4,7,12‐trione ring system have been prepared by the reaction of 3‐amino‐1‐aryl‐5,10‐dioxo‐5,10‐dihydro‐1H‐pyrazolo[1,2‐b]phthalazine‐2‐carbonitriles with aliphatic carboxylic acids in the presence of phosphoryl chloride (POCl3). The synthesized compounds were characterized on the basis of IR, 1H NMR, and 13C NMR spectral and microanalytical data.

Facile Synthesis of New 6‐Alkylamino‐1H‐pyrazolo[3,4‐b]pyridine‐5‐carbonitrile Derivatives

“…Taking all these facts into consideration, and in conjunction with our earlier studies of synthesis of heterocyclic compounds , herein, we report the synthesis of some new derivatives of 6‐alkylamino‐1,3‐diphenyl‐1 H ‐pyrazolo[3,4‐ b ]pyridine‐5‐carbonitrile 4a–f in synthetically useful yields by Knoevenagel condensation of 5‐chloro‐1,3‐diphenyl‐1 H ‐pyrazole‐4‐carbaldehyde 1 with malononitrile 2 in ethanol containing a few drops of glacial acetic acid at reflux temperature, which afforded compound 3 , followed by cyclization with primary alkyl amines in the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) as catalyst in refluxing ethanol (Scheme ). To the authors' knowledge, compounds 4a–f are new and have not been reported in the literature.…”