[NH2:1][C:2]1[CH:7]=[N:6][C:5]([Br:8])=[CH:4][N:3]=1.ClCCl.N1C=CC=CC=1.[CH3:18][C:19]([CH3:24])([CH3:23])[C:20](Cl)=[O:21]>C(O)C>[Br:8][C:5]1[N:6]=[CH:7][C:2]([NH:1][C:20](=[O:21])[C:19]([CH3:24])([CH3:23])[CH3:18])=[N:3][CH:4]=1A 3-necked 1 L round bottomed flask equipped with a magnetic stirrer, thermometer, condenser and nitrogen inlet/outlet was charged with 50.00 g (287.4 mmol) of 2-amino-5-bromopyrazine (1), 218 mL of dichloromethane and 30.50 mL (377.1 mmol) of pyridine. Then, 39.30 mL (319.1 mmol) of trimethylacetyl chloride (PivCl) was added dropwise over 5 min. An exotherm ensued that raised the temperature of the mixture from 22° C. to 44° C. After stirring at ca. 40° C. for 2 h, HPLC analysis indicated complete reaction. The reaction mixture was diluted with 200 mL of ethanol, then concentrated by distillation at atmospheric pressure. After 240 mL of distillate had collected and the temperature of the mixture reached 68° C., 100 mL of water was added slowly, while maintaining the temperature of the mixture at ca. 68° C. After the addition was complete, the resulting suspension was allowed to cool to room temperature and stirred overnight. The solid was collected by filtration, washed with 100 mL of ethanol:water 1:1 and dried by suction to give 67.08 g (90.4% yield) of the title compound as a light beige solid; 98.21% pure as determined by HPLC analysis (HPLC column Zorbax Eclipse XDB-C8, 4.6×50 mm, 1.8 μm, eluent 5-100% acetonitrile/water+01. % TFA over 5 min at 1 mL/min, detection at UV 250 nm, retention time 4.22 min).
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