[Cl:1][C:2]1[C:3]([NH:8][NH:9][C:10](=[O:15])[C:11]([F:14])([F:13])[F:12])=[N:4][CH:5]=[CH:6][N:7]=1.N1C=CC=CC=1.[Br:22]Br.O>CC(O)=O>[Br:22][C:6]1[N:7]=[C:2]([Cl:1])[C:3]([NH:8][NH:9][C:10](=[O:15])[C:11]([F:12])([F:13])[F:14])=[N:4][CH:5]=1A solution of 2.40 g of the product of Step A and 1.97 g of pyridine in AcOH (10.0 mL) at 0° C. was stirred as a solution of 1.92 g of bromine in AcOH (1.0 mL) was added dropwise. The resulting mixture was stirred at 0° C. for one h and then warmed to ambient temperature and stirred for an additional 16 h. The reaction mixture was poured into water and extracted with EtOAc (2×). The combined organic extracts were washed with water, dried over magnesium sulfate, filtered, and concentrated to an oil that was purified by silica gel chromatography to provide trifluoroacetic acid N′-(5-bromo-3-chloro-pyrazin-2-yl)-hydrazide as a white solid. MS (M+H+)=320.1.
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