Synthesis, characterization and antioxidant activity studies of new coumarin tethered 1,3,4-oxadiazole analogues

The present work describes the synthesis of a series of substituted 3-(5-phenyl-1,3,4-oxadiazol-2-yl)-2H-chromen-2-ones 7(a–j) using substituted aldehydes with analogues of hydrazine hydrates by grinding technique in the presence of Iodine which helps in the cyclization process. The structures of the synthesized compounds were elucidated by spectroscopic techniques such as IR, 1H NMR, 13C NMR, and LCMS. The comparative antioxidant property (using DPPH and hydroxyl radical scavenging) has been studied with the synthesized compounds 7(a-j) and the standards. Compounds 7d and 7i show the prominent radical scavenging activity. Synopsis: Series of ten new coumarin-oxadiazole hybrids synthesized in three steps starting from salicylaldehyde and diethylmalonate. All new compounds were spectroscopically characterized. The results of radical scavenging activities show that, two compounds of the series 7d and 7i displayed potent DPPH and hydroxyl radical activity comparable to the standards employed, and therefore acts as antioxidant leads.