[CH:1]1[C:6]2[CH2:7][CH2:8][CH2:9][CH2:10][C:11](=[O:12])[C:5]=2[CH:4]=[CH:3][CH:2]=1.[Al+3].[Cl-].[Cl-].[Cl-].N#N.[Br:19]Br>Cl>[Br:19][C:1]1[C:6]2[CH2:7][CH2:8][CH2:9][CH2:10][C:11](=[O:12])[C:5]=2[CH:4]=[CH:3][CH:2]=1.[Br:19][C:3]1[CH:2]=[CH:1][C:6]2[CH2:7][CH2:8][CH2:9][CH2:10][C:11](=[O:12])[C:5]=2[CH:4]=1
6,7,8,9-tetrahydro-5H-benzo[7]annulen-5-one (8 g, 50 mmol) was added to a flask containing AlCl3 (16.6 g, 125 mmol) dropwise under N2 and the mixture was stirred at r.t. for 30 minutes, and then Br2 (3 mL, 60 mmol) was added dropwise and the mixture was heated to 80° C. for another 5 minutes. Then the mixture was poured into a mixture of conc. HCl (20 mL) and ice (200 g) and stirred for 10 minutes. Then the mixture was extracted with MTBE and the organic layer was washed with aq. NaHCO3 and brine, dried, filtered and concentrated. The residue was purified by silica gel chromatography to give 1-bromo-6,7,8,9-tetrahydro-5H-benzo[7]annulen-5-one (6 g, crude) and 3-bromo-6,7,8,9-tetrahydro-5H-benzo[7]annulen-5-one (4 g, crude), which were used for next step directly.
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