[Al+3].[Cl-].[Cl-].[Cl-].[CH3:5][C:6]1([CH3:17])[C:10]2[CH:11]=[C:12]([CH:15]=[O:16])[CH:13]=[CH:14][C:9]=2[O:8][CH2:7]1.[Br:18]Br.Cl>ClCCl>[Br:18][C:14]1[C:9]2[O:8][CH2:7][C:6]([CH3:17])([CH3:5])[C:10]=2[CH:11]=[C:12]([CH:15]=[O:16])[CH:13]=1To a solution of AlCl3 (1.22 g, 9.18 mmol) in dry dichloromethane (15 mL) was added dropwise at room temperature 3,3-dimethyl-2,3-dihydro-benzofuran-5-carbaldehyde (647 mg, 3.67 mmol) in dichloromethane (15 mL) followed by bromine (0.23 mL, 4.41 mmol) and the reaction stirred for 3 hours. 1N HCl was added slowly and the layers separated. The aqueous layer was extracted twice with dichloromethane. The combined organic layers were washed successively with water and brine, dried over anhydrous magnesium sulfate, filtered and evaporated. The residue was chromatographed on silica gel (20% ethyl acetate in hexane) to give 856 mg of 7-bromo-3,3-dimethyl-2,3-dihydro-benzofuran-5-carbaldehyde (91%). 1H NMR (300 MHz; CDCl3): 1.40(s, 6H), 4.46 (s, 2H), 7.61 (s, 1H), 7.83 (s, 1H), 9.80 (s, 1H).
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