[CH3:1][C:2]1[C:3]([C:8](=[O:10])[CH3:9])=[N:4][CH:5]=[CH:6][N: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:3]1[C:2]([CH3:1])=[N:7][CH:6]=[CH:5][N:4]=1)=[O:10]To a chloroform (7.5 mL) solution of 1-(3-methylpyrazin-2-yl)ethanone (0.50 g), under ice cooling in a nitrogen atmosphere, 2,6-lutidine (0.75 mL) and trimethylsilyl trifluoromethanesulfonate (0.80 mL) were added, and the resultant was stirred for 30 minutes. Then, N-bromosuccinimide (0.73 g) was added thereto, and the resultant was stirred for 1 hour under ice cooling. Water was added to the reaction solution, and the resultant was stirred for 10 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=95/5→85/15) to obtain the title compound (0.58 g) as a brown solid.
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