[C:1](=O)([O-])[O-].[Cs+].[Cs+].BrC[CH2:9][CH:10]1O[CH2:13][CH2:12][O:11]1.CN(C)[CH:17]=[O:18].[Cl:20][C:21]1[CH:22]=[C:23]([OH:28])[CH:24]=[N:25][C:26]=1[F:27]>O>[Cl:20][C:21]1[C:26]([F:27])=[N:25][CH:24]=[C:23]([O:28][CH2:9][CH:10]([O:18][CH2:17][CH3:1])[O:11][CH2:12][CH3:13])[CH:22]=1Cesium carbonate (2.9 g, 8.9 mmol) and 2-(2-bromoethyl)-1,3-dioxolane (990 mg, 5.0 mmol) were added to an N,N-dimethylformamide suspension (10 ml) of 5-chloro-6-fluoropyridin-3-ol (570 mg, 3.9 mmol), and stirred at 100° C. for 4 hours. The reaction solution was cooled to room temperature, water was added, and extracted with ethyl acetate. The organic layer was washed with water and saturated saline water, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The obtained residue was purified by silica gel column chromatography (hexane:ethyl acetate=70:30) to obtain 3-chloro-5-(2,2-diethoxyethoxy)-2-fluoropyridine (640 mg, yield: 62%) as a colorless oil.
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