Br[C:2]1[CH:7]=[C:6]([O:8][CH3:9])[CH:5]=[C:4]([Br:10])[CH:3]=1.[Li]CCCC.CN([CH:19]=[O:20])C.O>CCOCC>[Br:10][C:4]1[CH:3]=[C:2]([CH:7]=[C:6]([O:8][CH3:9])[CH:5]=1)[CH:19]=[O:20]A solution of 1,3-dibromo-5-methoxybenzene (15 g, 56.40 mmol) in anhydrous Et2O (200 mL) under nitrogen was cooled to −78° C. n-BuLi (38.80 mL of a 1.6 M solution in Et2O, 62.00 mmol) was added dropwise, and the solution was aged at −78° C. for 45 m. To the resulting heterogeneous mixture was added anhydrous DMF (4.78 mL, 62.00 mmol), and the solution was slowly warmed to RT. The mixture was poured into H2O (200 mL), and the aqueous phase was extracted with Et2O (3×125 mL). The combined organic fractions were washed with brine (100 mL) and dried over anhydrous MgSO4. Evaporation of the solvent provided 11.70 g (96%) of 3-bromo-5-methoxybenzaldehyde (115).
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