[CH3:1][O:2][CH:3]([O:17][CH3:18])[CH2:4][N:5]1[C:14]2[C:9](=[N:10][CH:11]=[C:12]([F:15])[CH:13]=2)[CH2:8][CH2:7][C:6]1=[O:16].BrN1C(=O)CCC1=O.C(=O)([O-])[O-].[K+].[K+].[OH-].[Na+]>ClC1C=CC=CC=1.N(C(C)(CC(OC)(C)C)C#N)=NC(C)(CC(C)(OC)C)C#N.O>[CH3:18][O:17][CH:3]([O:2][CH3:1])[CH2:4][N:5]1[C:14]2[C:9](=[N:10][CH:11]=[C:12]([F:15])[CH:13]=2)[CH:8]=[CH:7][C:6]1=[O:16]To a suspension of 5.0 g of 1-(2,2-dimethoxyethyl)-7-fluoro-3,4-dihydro-1,5-naphthyridin-2(1H)-one, 5.3 g of N-bromosuccinimide and 3.0 g of potassium carbonate in 30 mL of chlorobenzene, 0.12 g of 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) was added three times hourly at 50 to 60° C. under a nitrogen atmosphere. After stirring the reaction mixture for 1 hour at the same temperature, 10 mL of water was added thereto, and the mixture was adjusted to pH 12.6 using a 20% sodium hydroxide solution. The organic layer was separated and washed with 15 mL of water. The aqueous layer was extracted with 15 mL of toluene. The organic layer and the extract were combined to evaporate the solvent under reduced pressure. To the obtained residue, 2 mL of chlorobenzene and 6 mL of cyclohexane were added, the mixture was stirred for 30 minutes under ice cooling, and the solid product was obtained by filtration and washed with cyclohexane to give 4.1 g of 1-(2,2-dimethoxyethyl)-7-fluoro-1,5-naphthyridin-2(1H)-one as a light yellow solid.
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