[CH3:1][N:2]1[C:7]2[CH:8]=[CH:9][CH:10]=[CH:11][C:6]=2[O:5][CH2:4][CH2:3]1.[Br:12]N1C(=O)CCC1=O>CN(C=O)C.C(Cl)Cl>[Br:12][C:10]1[CH:9]=[CH:8][C:7]2[N:2]([CH3:1])[CH2:3][CH2:4][O:5][C:6]=2[CH:11]=1A mixture of the 104B (0.225 g, 1.51 mmol) and N-bromosuccinimide (0.269 g, 1.51 mmol) in DMF (10 mL) was heated at 80° C. overnight. The reaction mixture was dissolved in DCM and washed with water several times. The organic layer was collected, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel chromatography to give 0.267 g (78%) of 104C. HPLC retention time=3.32 min. (Condition B) and LC/MS M+1=230.03 (d). 1H-NMR (500 MHz, CDCl3) δ 2.83 (s, 3H), 3.22 (t, 2H), 4.26 (t, 2H), 6.49 (d, 1H, J=8.8 Hz), 6.87 (s, 1H), and 6.90 (d, 1H, J=8.8 Hz).
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