[N:1]1[CH:6]=[CH:5][C:4]([C:7]2[N:17]=[C:11]3[CH2:12][CH2:13][O:14][CH2:15][CH2:16][N:10]3[C:9](=[O:18])[CH:8]=2)=[N:3][CH:2]=1.C[Si]([N-][Si](C)(C)C)(C)C.[Li+].[Br:29]Br>O1CCCC1>[Br:29][CH:12]1[C:11]2=[N:17][C:7]([C:4]3[CH:5]=[CH:6][N:1]=[CH:2][N:3]=3)=[CH:8][C:9](=[O:18])[N:10]2[CH2:16][CH2:15][O:14][CH2:13]1To a solution of 5.00 g (20.47 mmol) of pyrimidin-4-yl-5,6,8,9-tetrahydro-7-oxa-1,4a-diaza-benzocyclohepten-4-one in dry tetrahydrofuran (200 mL) under argon at −40° C. was added 22.52 mL (22.52 mmol) of lithium bis(trimethylsilyl)amide (1M in tetrahydrofuran). The solution was stirred at −40° C. for 10 min and 1.10 mL (21.49 mmol) of bromine was added rapidly. The reaction was stirred at −40° C. during 20 minutes and the reaction mixture was quenched with the addition of a saturated solution of ammonium chloride and extracted with ethyl acetate. The organic phase was washed with saturated sodium chloride solution and dried over sodium sulfate and concentrated. The residue was purified by flash chromatography (cyclohexane/ethyl acetate: 80/20 to 70/30) to afford 2.18 g (33%) of product.
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