Synthesis and antioxidant activity of styryl-1,3,4-thiadiazoles, pyrazolyl-1,3,4-thiadiazoles and isoxazolyl-1,3,4-thiadiazoles

A new class of sulfonamido methyl linked styrylsulfonylmethyl-1,3,4-thiadiazoles, pyrazolyl and isoxazolyl 1,3,4-thiadiazoles have been synthesized from the synthetic intermediate 2-(arylaminosulfonylmethyl)-5-(Z-(styrylsulfonylmethyl))-1,3,4-oxadiazole and studied their antioxidant activity. Amongst all the compounds, 2-((p-methylphenyl)aminosulfonylmethyl)-5-((3'-phenyl-5'-(p-methylphenyl)isoxazol-4'-ylsulfonyl)methyl)-1,3,4-thiadiazole (6b) exhibits promising antioxidant activity. Compounds having thiadiazole and isoxazole moieties show higher radical scavenging activity. Moreover, electron donating methyl substitution on phenyl ring enhances the antioxidant activity as compared to chloro and unsubstituted compounds.