Antimicrobial studies of some novel quinazolinones fused with [1,2,4]-triazole, [1,2,4]-triazine and [1,2,4,5]-tetrazine rings

Three series of novel and new fused heterocyclic systems, viz. triazolo[4,3-a]-quinazolin-7-ones (4), [1,2,4,5]-tetrazino[4,3-a]-quinazolin-8-ones (6) and indolo[2,3-c][1,2,4]-triazino[4,3-a]-quinazolin-8-ones (8) have been synthesized from the key intermediate 3-(substituted-phenyl)-2-hydrazino-quinazolin-4-ones (3). Thus, condensation of (3) with appropriate aromatic acids in the presence of DCC in dichloromethane afforded the fused system (4), while reaction of (3) with isatin in methanol gave the corresponding Schiff base (7) which on cyclodehydration furnished another fused heterocyclic system (8). The intermediate (3) on refluxing with substituted-phenylisothiocyanate gave the substituted-thiosemicarbazide (5), which on oxidative cyclization with bromine in CCl4 furnished the novel fused system (6). The structures of intermediate and final compounds have been determined by means of IR, 1H NMR, 13C NMR, UV and elemental analysis. All the synthesized compounds have been screened for their antibacterial activity against Gram-negative bacteria, Escherichia coli, Pseudomonas aeruginosa and Gram-positive bacteria, Streptococcus pneumoniae, Bacillus subtilis, as well as demonstrated significant antifungal activity against fungi viz. Candida albicans, Aspergillus fumigatus, Aspergillus flavus, and Aspergillus niger.

Graphical abstractThree series of novel quinazolinones derivatives were synthesized and screened for their antimicrobial activity against bacterial and fungal strain. The synthesized compounds showed good antimicrobial activity against both bacterial and fungal strain. The results suggest that these compounds to be potent antimicrobial agents.Figure optionsDownload full-size imageDownload as PowerPoint slide