P(Cl)(Cl)([Cl:3])=O.[F:6][C:7]1[CH:8]=[N:9][CH:10]=[CH:11][C:12]=1[C:13]1[N:18]=[C:17](S)[N:16]([CH3:20])[C:15](=[O:21])[CH:14]=1>CN(C)C=O>[Cl:3][C:17]1[N:16]([CH3:20])[C:15](=[O:21])[CH:14]=[C:13]([C:12]2[CH:11]=[CH:10][N:9]=[CH:8][C:7]=2[F:6])[N:18]=1After one hour stirring of a solution of phosphorus oxychloride (45 g, 293 mmol) in dimethylformamide (450 ml) at room temperature, 6-(3-fluoropyridin-4-yl)-2-mercapto-3-methyl-3H-pyrimidin-4-one (46.3 g, 195 mmol) was added and heated at 60° C. for 2 hours. The resulting suspension was partitioned between ethyl acetate and saturated aqueous sodium bicarbonate. The aqueous layer was extracted with ethyl acetate and the combined organic layer was washed with brine, dried over magnesium sulfate, and concentrated in vacuo. The residue was washed by hexane to furnish 2-chloro-6-(3-fluoropyridin-4-yl)-3-methyl-3H-pyrimidin-4-one (34.2 g, 143 mmol, 73%) as white crystals.
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