We have synthesized mannich bases 1,3,4 oxadiazoles-2-thione using microwave irradiation method, and studied their pharmacological activity. A series of 2, 5 - disubstituted - l, 3, 4 - oxadiazoles were synthesized by refluxing 2-furoic acid with ethanol and conc. H2SO4. The obtained ester (2) with hydrazine hydrate and ethanol was refluxed to give hydrazides (3), reactions of hydrazides (3) with different aromatic acids lead to the formation of 5- furyl- 2-aryl -1, 3, 4-oxadiazoles [R(1-3)]. The hydrazides (3) were also converted to 5-furyl-3- arylmethyl -1,3,4- oxadiazole -2- thione (4) in presence of carbon disulphide and potassium hydroxide . Subsequent reaction of thione with primary or secondary amines in presence of formaldehyde gave the Mannich bases [D (1-3)] by conventional and microwave techniques. The efficiency of microwave assisted organic synthesis has dramatically reduced reaction time and structures were characterized on the basis of IR, NMR and Mass Spectral analysis. All the compounds were screened for in vitro antioxidant activity by DPPH assay method and they have shown positive anti-oxidant activity.
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