[Cl:1][C:2]1[N:7]=[C:6]([C:8]#[N:9])[C:5]([N+:10]([O-:12])=[O:11])=[CH:4][CH:3]=1.[OH:13]S(O)(=O)=O>>[Cl:1][C:2]1[N:7]=[C:6]([C:8]([NH2:9])=[O:13])[C:5]([N+:10]([O-:12])=[O:11])=[CH:4][CH:3]=16-chloro-2-cyano-3-nitropyridine (9.50 g, 51.76 mmol) is taken up in 150 mL of 90% H2SO4 solution. The reaction mixture is stirred for 4 h at 70° C., cooled and slowly added dropwise to ice water. The precipitate formed is filtered off, washed with water and dried. The aqueous filtrate is extracted 6× with DCM. The organic phases are combined, dried on Na2SO4, filtered off and concentrated by rotary evaporation. The residue is mixed with the precipitate, dried overnight at 50° C. in the drying cupboard and 6-chloro-3-nitro-pyridine-2-carboxylic acid amide (HPLC-MS: tRet.=0.43 min; MS (M+H)+=202) is obtained.
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