[Br:1][C:2]1[CH:9]=[C:6]([CH:7]=O)[C:5]([OH:10])=[CH:4][CH:3]=1.Cl[CH2:12][C:13](=[O:15])[CH3:14].C([O-])([O-])=O.[Cs+].[Cs+].O>CN(C=O)C>[C:13]([C:14]1[O:10][C:5]2[CH:4]=[CH:3][C:2]([Br:1])=[CH:9][C:6]=2[CH:7]=1)(=[O:15])[CH3:12]A mixture of 5.0 g (24.9 mmol) of 5-bromo-salicylaldehyde, 3.0 g (32.3 mmol, 2.6 mL) of chloroacetone and 12 g (37.2 mmol) of Cs2CO3 in 30 mL of dry DMF was heated to 60° C. overnight. After cooling at room temperature, water (100 mL) was added and the mixture was extracted with ethyl acetate. The organic layer was dried over MgSO4 and the solvents were removed under reduced pressure. The crude product was directly recrystallized from hexane to afford 4.14 g (17.3 mmol, yield: 70%) of 2-acetyl-5-bromo benzo[b]furan as a pale orange crystal. 1H NMR (CDCl3), δ: 7.84 (d, J=1.9 Hz, 1H), 7.56 (dd, J=9.0, 2.1 Hz, 1H), 7.45 (d, J=8.9 Hz, 1H), 7.42 (s, 1H), 2.60 (s, 3H).
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