in Wiley Online Library (wileyonlinelibrary.com).Some new derivatives of 6-alkylamino-1,3-diphenyl-1H-pyrazolo[3,4-b]pyridine-5-carbonitrile have been prepared through a Knoevenagel condensation reaction of 5-chloro-1,3-diphenyl-1H-pyrazole-4-carbaldehyde with malononitrile in ethanol containing a few drops of glacial acetic acid at reflux temperature followed by cyclization with primary alkyl amines in the presence of 1,8-diazabicyclo[5.4.0] undec-7-ene as catalyst in refluxing ethanol. The products were characterized on the basis of IR, 1 H NMR, and 13 C NMR spectral and microanalytical data. The 1 H NMR data ruled out the formation of the alternative cyclized isomers 6-imino-7-alkyl-1,3-diphenyl-6,7-dihydro-1H-pyrazolo[3,4-b]pyridine-5-carbonitriles.
Some new 7-alkyl-4,6-dihydropyrazolo[4′,3′:5,6]pyrano[2,3-d]pyrimidin-5(1H)-ones were prepared through heterocyclization of 6-amino-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles with aliphatic carboxylic acids in the presence of phosphoryl chloride under reflux in high yields. The suggested mechanism involves a tandem intramolecular Pinner–Dimroth rearrangement. The products were characterized on the basis of FT-IR, 1H NMR, and 13C NMR spectral and microanalytical data and evaluated for their antibacterial activity against Gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) using the disk diffusion method.
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