Facile synthesis of new pyrazolo[4′,3′:5,6]pyrano[2,3-d]pyrimidin-5(1H)-ones via the tandem intramolecular Pinner–Dimroth rearrangement and their antibacterial evaluation

Abstract

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.

Recent Synthesis of Mono‐ & Bis‐Pyranopyrazole Derivatives

“…[5,6] It has other alternative names such as pyrano [2,3c]pyrazoles, 4H-pyrano [2,3-c]pyrazoles and also 1,4dihydropyrano [2,3-c]pyrazol-5-yl cyanides. [7,8] Pyranopyrazole is a bioactive moiety [9] that has numerous applications in pharmaceuticals and agrochemicals, herbicide, fungicide, [10] insecticide, [11] larvicidal, [12] and biological activities i. e., antibacterial, [13][14][15] antimicrobial, [16] anticancer, [17][18][19][20] antitubercular, [21] antiallergenic, [22] antioxidant, [23,24] antineoplastic, [25] , anti-inflammatory, [26] and human Chk1 kinase inhibitor activities (Figure 2). [3,[27][28][29] The stability of pyranopyrazoles depends on substituent rings and intermolecular hydrogen bonding interactions between the molecules.…”