[Cl:1][C:2]1[C:7](=[O:8])[NH:6][CH:5]=[C:4]([C:9]([O:11][CH3:12])=[O:10])[CH:3]=1.[H-].[Na+].FS([C:19](C(O)=O)([F:21])[F:20])(=O)=O.O>CC#N>[Cl:1][C:2]1[C:7]([O:8][CH:19]([F:21])[F:20])=[N:6][CH:5]=[C:4]([CH:3]=1)[C:9]([O:11][CH3:12])=[O:10]
A mixture of methyl 5-chloro-6-oxo-1,6-dihydropyridine-3-carboxylate (3.810 g; 20.31 mmol) in anh. MeCN (400 ml) was treated portionwise with NaH (60% dispersion in mineral oil; 2.193 g; 54.84 mmol), and stirring at rt, under nitrogen, was continued for 20 min. FSO2CF2CO2H (6.149 g; 34.52 mmol) was then added dropwise, and the resulting heterogeneous mixture was further stirred at rt, under nitrogen, for 45 min. Water (10 ml) was slowly added, and MeCN was removed under reduced pressure. Water (150 ml) and AcOEt (150 ml) were added, and the separated aq. layer was further extracted with AcOEt (3×100 ml). The mixed organic layers were dried over anh. MgSO4, filtered, and concentrated to dryness under reduced pressure. Purification by FC (DCM) afforded methyl 5-chloro-6-(difluoromethoxy)nicotinate as an off-white solid. LC-MS (conditions A): tR=0.81 min.; no ionisation.
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