[K+].[Br:2][C:3]1[CH:8]=[C:7]([CH3:9])[N:6]=[C:5]([C:10]([O-:12])=[O:11])[CH:4]=1.[CH2:13](O)[CH3:14]>OS(O)(=O)=O.C([O-])(O)=O.[Na+]>[CH2:13]([O:11][C:10]([C:5]1[CH:4]=[C:3]([Br:2])[CH:8]=[C:7]([CH3:9])[N:6]=1)=[O:12])[CH3:14]To a suspension of 4-bromo-6-methyl-pyridine-2-carboxylic acid potassium salt (253 mg, 0.996 mmol) in ethanol (100 mL), H2SO4 (2 mL) is added dropwise. The mixture is heated to 70° C. for 16 h before it is carefully diluted with sat. aq. NaHCO3. The mixture is extracted three times with diethyl ether. The combined org. extracts are dried over MgSO4, filtered and concentrated. The crude product is purified on prep. TLC plates with heptane:EA 3:2 to give 4-bromo-6-methyl-pyridine-2-carboxylic acid ethyl ester (105 mg) as a pale yellow oil; LC-MS: tR=0.85 min, [M+1]+=244.22.
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