[CH3:1][C:2]1[C:7]([C:8]([C:10](=[CH:16][NH:17][CH:18]2[CH2:20][CH2:19]2)[C:11]([O:13][CH2:14][CH3:15])=[O:12])=[O:9])=[C:6](F)[C:5]([F:22])=[C:4]([F:23])[C:3]=1[F:24].[H-].[Na+]>O1CCOCC1>[CH:18]1([N:17]2[C:6]3[C:7](=[C:2]([CH3:1])[C:3]([F:24])=[C:4]([F:23])[C:5]=3[F:22])[C:8](=[O:9])[C:10]([C:11]([O:13][CH2:14][CH3:15])=[O:12])=[CH:16]2)[CH2:20][CH2:19]1Ethyl 2-(6-methyl-2,3,4,5-tetrafluorobenzoyl)-3-cyclopropylaminoacrylate (4.50 g) is dissolved in anhydrous dioxane (26 ml) and thereto 60% sodium hydride (580 mg) is gradully added under ice-cooling. After stirring at room temperature for 30 minutes, the reaction mixture is poured into ice-water and extracted with dichloromethane. The extract is dried over magnesium sulfate and concentrated. The residue is added with diethyl ether and crystals are filtered, which are recrystalized from dichloromethane-n-hexane to give ethyl 1-cyclopropyl-6,7,8-trifluoro-5-methyl-1,4-dihydro-4-oxoquinoline-3-carboxylate (4.19 g), as white needles, m.p. 180°-183° C.
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