[N+:1]([O-:4])(O)=[O:2].[CH3:5][O:6][C:7](=[O:20])[C:8]1[CH:13]=[CH:12][C:11]([Cl:14])=[N:10][C:9]=1[O:15][CH2:16][CH:17]([F:19])[F:18]>OS(O)(=O)=O>[CH3:5][O:6][C:7](=[O:20])[C:8]1[CH:13]=[C:12]([N+:1]([O-:4])=[O:2])[C:11]([Cl:14])=[N:10][C:9]=1[O:15][CH2:16][CH:17]([F:19])[F:18]Fuming HNO3 (25 mL) is added at rt to 6-chloro-2-(2,2-difluoro-ethoxy)-nicotinic acid methyl ester (10.7 g, 42.5 mmol) in concentrated H2SO4 (50 mL) and stirred for 10 min. The reaction mixture is added dropwise to ice water, stirred and filtered. The filtercake is washed with water and dried at 50° C.
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