[NH2:1][C:2]1[N:12]=[C:11]([NH:13][C:14](=[O:19])[C:15]([CH3:18])([CH3:17])[CH3:16])[CH:10]=[CH:9][C:3]=1[C:4]([O:6][CH2:7][CH3:8])=[O:5].[Cl:20]Cl>C(O)(=O)C>[NH2:1][C:2]1[N:12]=[C:11]([NH:13][C:14](=[O:19])[C:15]([CH3:18])([CH3:17])[CH3:16])[C:10]([Cl:20])=[CH:9][C:3]=1[C:4]([O:6][CH2:7][CH3:8])=[O:5]To a solution of ethyl 2-amino-6-[(2,2-dimethylpropanoyl)amino]nicotinate (Example 1, METHOD A, Step 1, 805 mg, 3.03 mmol) in acetic acid (15 ml) was added a solution of chlorine in acetic acid (0.89 M, 8.5 mL, 7.6 mmol), and the mixture was stirred at room temperature for 15 min. The solvent was removed in vacuo. The obtained residue was taken up in ethyl acetate (150 mL) and washed with saturated sodium bicarbonate, dried over magnesium sulfate, and evaporated in vacuo. The residue was chromatographed on a column of silica gel eluting with ethyl acetate/pentane (1:2) to give 685 mg (76%) of the title compound as a white crystal.
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