Facile synthesis of new pyrazolo4 ',3 ':5,6pyrano2,3-d pyrimidin-5(1H)-ones via the tandem intramolecular Pinner-Dimroth rearrangement and their antibacterial evaluation

摘要

Some new 7-alkyl-4,6-dihydropyrazolo4',3':5,6 pyrano2,3-dpyrimidin-5(1H)-ones were prepared through heterocyclization of 6-amino-1,4-dihydropyrano2,3-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, H-1 NMR, and C-13 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.