Design and Synthesis of Novel Quinazolin-4(3H)-One Appended 1,2,4-Oxadiazoles as Antimicrobial Agents

A novel series of hybrid heterocycles having quinazolinone based 1,2,4-oxadiazoles scaffold with methylamino linkage were obtained in two synthetic pathways. In method I, quinazolinone based ester reacted with amidoximes and gave the corresponding hybrid products in poor yields. To reduce the duration of reaction time and increase the yields of the products, dehydrochlorination reaction of 6-aminoquinazolinone was carried out with 5-chloromethyl-1,2,4-oxadiazoles in other synthetic method, which furnished the products in good to excellent yields. The synthesized 1,2,4-oxadiazole hybrids were characterized using spectroscopic techniques and also screened for their antimicrobial activity against bacteria and fungi, among which chloro-substituted analogues 6d and 6e presented potent activity against all strains whereas other analogues proven to have moderate activities.