[CH3:1][C:2]1[N:3]=[CH:4][C:5]([C:8](=[O:10])[CH3:9])=[N:6][CH:7]=1.N1C(C)=CC=CC=1C.FC(F)(F)S(O[Si](C)(C)C)(=O)=O.[Br:31]N1C(=O)CCC1=O>O.C(Cl)(Cl)Cl>[Br:31][CH2:9][C:8]([C:5]1[CH:4]=[N:3][C:2]([CH3:1])=[CH:7][N:6]=1)=[O:10]
To a chloroform (28 mL) solution of 1-(5-methylpyrazin-2-yl)ethanone (1.9 g), under ice cooling in a nitrogen atmosphere, 2,6-lutidine (2.7 mL) and trimethylsilyl trifluoromethanesulfonate (3.0 mL) were added, and the resultant was stirred for 30 minutes. Then, N-bromosuccinimide (3.0 g) was added thereto, and the resultant was stirred at room temperature for 1 hour. Water was added to the reaction solution, and the resultant was stirred for 15 minutes, followed by extraction with chloroform. An organic layer was separated using a phase separator, and the solvent was distilled off under reduced pressure. The obtained residue was purified by silica gel column chromatography (OH-type silica gel; hexane/ethyl acetate-gradient elution=90/10→60/40) and then further purified by hexane/ethyl acetate-gradient elution (=90/10→80/20) to obtain the title compound (2.1 g) as a pale yellow solid.
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