Synthesis and evaluation of antioxidant and antibacterial activities of new substituted bis(1,3,4-oxadiazoles), 3,5-bis(substituted) pyrazoles and isoxazoles

Two series of five membered heterocyclic bis(1,3,4-oxadiazole) derivatives 2(a-h) and 3,5-bis(substituted) pyrazoles, isoxazoles 3(a, b, d-i), 4(a-c) were synthesized via oxidative cyclization of some diaroylhydrazones using chloramine-T and cyclocondensation reaction with hydrazine hydrate and hydroxylamine hydrochloride, respectively. The newly synthesized compounds were screened for antioxidant and anti-microbial activities. Compounds 2(b), 3(b), and 4(a) showed higher antioxidant activity at 10 mu g/ml while compounds 2(a), 3(a), 3(f), and 4(a) exhibited better anti-microbial activity at 100 mu g/ml compared with standard vitamin C and ciprofloxacin, respectively. Structures of newly synthesized compounds were confirmed by elemental analysis and spectral IR, H-1 NMR, and C-13 NMR data. (C) 2011 Elsevier Ltd. All rights reserved.