[CH3:1][O:2][C:3]1[CH:12]=[C:11]([CH3:13])[CH:10]=[CH:9][C:4]=1[C:5]([O:7][CH3:8])=[O:6].CC(O)=O.[Br:18]Br.C([O-])([O-])=O.[Na+].[Na+]>O>[Br:18][C:10]1[C:11]([CH3:13])=[CH:12][C:3]([O:2][CH3:1])=[C:4]([CH:9]=1)[C:5]([O:7][CH3:8])=[O:6]
A 250 ml 3-neck RBF fitted with a magnetic stirring bar, a thermometer and a dropping funnel was charged with methyl 2-methoxy-4-methylbenzoate 10b (10 g, 0.056 mol) and AcOH (70 mL). To this solution bromine (3 mL, 0.06 mol) was added drop-wise while maintaining the reaction temperature below 25° C. When bromine addition was complete, the reaction mixture was stirred at RT for 2 hours, then poured into 600 mL of cold water and the pH was adjusted to 8-9 with Na2CO3. The crude product was extracted with Et2O (3×300 mL), the combined extracts washed with brine, dried over sodium sulfate and the solvent was removed under vacuum to give methyl 5-bromo-2-methoxy-4-methylbenzoate as an orange oil, which solidified on standing (14.3 g, 99% yield, >90% purity by 1H NMR).
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