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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.

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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.

Cesium carbonate can readily be separated from the reaction mixture and reused at least three times without significant loss of activity.