Eco-benign mediated versatile synthesis of newer quinazolin-4- (3H)-one clubbed isatin derivatives as potent antimicrobial agents

Abstract

A series of synthons consisting of a heterocyclic core flanked by two basic functionalities isatin and quinazolin-4-(3H)-one were synthesized using environmentally benign procedure and screened for in vitro antimicrobial activity. Neat reactants on subjecting to microwave irradiation gave the target products more quickly and in better yields. Benzoylation of anthranilic acid afforded the 2-phenyl-4H-benzo-(1,3)-oxazin-4-one I. The latter undergoes condensation with urea resulted in the formation of 4-oxo-2- phenyl quinazolin-4-(3H)-carboxamide II, which further undergoes condensation with isatin yielded the corresponding 4-oxo-N-(2-oxindolin-3-ylidene)-2-phenylquinazolin-4-(3H)-carboxamide III. This synthesized scaffolds were reacted under mannich condition to get the corresponding mannich bases of N-(1-substituted-2-oxoindolin-3-ylidene)-4-oxo-2-phenyl - quinazolin-4-(3H)carboxamide IVa-IVf. The chemical structures of all these title compounds have been confirmed by IR, ¹HNMR and mass spectral studies. Significant antimicrobial activities were observed for some members of the series.