5-Nitro-2-Furoic Acid → N2 4-[4-(4-ethyl-5-oxo-4,5-dihydro-1,3,4-oxadiazol-2-yl)piperi dino]phenyl-5-nitro-2-furamide

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5-[1-(4-Nitrophenyl)-4-piperidyl]-2,3-dihydro-1,3,4-oxadiazol-2-one (5a, 1.16 g, 4 mmol) on reacting with C2H5Br (0.53 g, 4.8 mmol) in DMF in the presence of base K2CO3 (1.38 g, 10 mmol) at room temperature (27° C.) for 10 h, after completion of the reaction, reaction mixture is poured into ice water and extracted into chloroform finally purification by column chromatography to afford pure compound 3-ethyl-5-[1-(4-nitro phenyl)-4-piperidyl]-2,3-dihydro-1,3,4-oxadiazol-2-one (6b, 1.17 g, 92%). Nitro compound (6b, 1.27 g, 4 mmol) on reduction with SnCl2.2H2O (2.71 g, 12 mmol) in methanol and refluxed at 65° C. for 4 h, after completion of reaction methanol is evaporated under vacuum and to this saturated sodium bicarbonate solution is added to quench the excess stannous chloride and filtered through celite bed and purified in silica column (60-120) to afforded pure compound 5-[1-(4-aminophenyl)-4-piperidyl]-3-ethyl-2,3-dihydro-1,3,4-oxadiazol-2-one (7c, 1.02 g, 89%). To a stirred solution of 5-nitro2-furanoic acid in DMF add HOBT (Hydroxybenzotriazole) (0.14 g, 1 mmol), EDCI (1-Ethyl-3-(3-dimethylaminopropyl)carbodi imide)) (0.19 g, 1 mmol) and amine compound (7c, 0.29g, 1 mmol) and stirred for 2 h at room temperature (27° C.), after completion of the reaction, reaction mixture is poured into ice water and extracted into chloroform finally purification by column chromatography using ethyl acetate-hexane (7:3) as eluant to afford pure compound N2-4-[4-(4-ethyl-5-oxo-4,5-dihydro-1,3,4-oxadiazol-2-yl)piperi dino]phenyl-5-nitro-2-furamide (8c, 367 mg, 86%).

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