Synthesis, structural characterization, and biological activity studies of novel pyrido [2,3-d]pyrimidines (10a−h, 11a−h) are described. Cyclization of cynoacetamides (4, 5) with malonitrile (7) and aldehyde (6a−h) via Hantzsch pyridine synthesis afforded cyanopyridones (8a−h, 9a−h), which on cyclization with formic acid under microwave conditions led to the final product. All the reactions are significantly faster and the isolated yields are remarkably higher in microwave conditions compared to the conventionally heated reactions. The compounds were tested in vitro for their antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtillus, Staphylococcus aureus, and Micrococcus luteus and antifungal activity against Trichphyton longifusus, Candida albicans, Microsporum canis, Fusarium solani. Compounds 10b, 10e, 11b and 11e exhibited good antibacterial and antifungal activities compared with standards.
A series of novel 2-amino-3-cyanothiophenes (2a-2j) were synthesized using heterogeneous base (K 2 CO 3) supported Gewald reaction. Cyclization of 2a-j with formamide and urea in conventional heating as well as microwave irradiation gave thieno[2,3-d]pyrimidines (3a-3j) and thieno[2,3-d]pyrimidin-2(1H)ones(4a-4j) respectively. The reaction rates were faster and yields were higher in the microwave conditions. The structures of the compounds were confirmed with elemental analysis, mass spectral analysis, FTIR, 1 H NMR and 13 C NMR techniques. All the synthesized compounds were subjected to antimicrobial activity (MIC) in vitro by broth dilution method and exhibited a moderate antimicrobial activity.
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