[F:1][C:2]1[CH:7]=[C:6]([N+:8]([O-])=O)[CH:5]=[CH:4][C:3]=1[N:11]1[C:15](=[O:16])[N:14]([CH:17]([F:19])[F:18])[C:13]([CH3:20])=[N:12]1.[H][H]>C(O)C.[Pt]=O>[F:1][C:2]1[CH:7]=[C:6]([NH2:8])[CH:5]=[CH:4][C:3]=1[N:11]1[C:15](=[O:16])[N:14]([CH:17]([F:19])[F:18])[C:13]([CH3:20])=[N:12]1A mixture of 24.5 g (0.085 mole) of 1-(2-fluoro-4-nitrophenyl)-4-difluoromethyl-4,5-dihydro-3-methyl-1,2,4-triazol-5(1H)-one and 0.30 g of platinum oxide in 250 mL of absolute ethanol was hydrogenated in a Parr hydrogenation apparatus. The calculated amount of hydrogen required was taken up in 45 minutes. The reaction mixture was filtered through a Buchner funnel, and the filtrate was evaporated under reduced pressure, leaving a dark brown solid residue. This residue was placed on a silica gel column and eluted with methylene chloride/ethyl acetate (75/25). After the product-containing fractions were combined, evaporation of the solvents under reduced pressure yielded 20.1 g of 1-(2-fluoro-4-aminophenyl)-4-difluoromethyl-4,5-dihydro-3-methyl-1,2,4-triazol-5(1H)-one. The NMR spectrum was consistent with the proposed structure.
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