[O:1]1[C:5]2[CH:6]=[CH:7][CH:8]=[N:9][C:4]=2[CH2:3][C:2]1=O.[OH-].[Na+].P(Cl)(Cl)([Cl:15])=O>>[Cl:15][C:2]1[O:1][C:5]2[CH:6]=[CH:7][CH:8]=[N:9][C:4]=2[CH:3]=1Furopyridone (6, 3.26 g, 24.15 mmol) is treated with phosphorus oxychloride (10 ml) at refluxing temperature for 3 hours. After cooling, the dark solution is poured into ice and basified with aqueous sodium hydroxide to pH ˜9. The mixture is extracted with chloroform. After evaporation of the chloroform, the brown oil is applied to flash column chromatography on silica gel to give chlorofuropyridine as yellow crystalline solid (7).
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