S(=O)(=O)(O)O.[K+].[Br:7][C:8]1[CH:13]=[C:12]([CH3:14])[N:11]=[C:10]([C:15]([O-:17])=[O:16])[CH:9]=1.C([O-])(O)=O.[Na+].[CH2:23](O)[CH3:24]>>[CH2:23]([O:16][C:15]([C:10]1[CH:9]=[C:8]([Br:7])[CH:13]=[C:12]([CH3:14])[N:11]=1)=[O:17])[CH3:24]Sulfuric acid (5 mL) is added to a suspension of 4-bromo-6-methyl-pyridine-2-carboxylic acid potassium salt (5.03 g, 15.5 mmol) in ethanol (150 mL). The clear solution is heated to 70° C. and stirred for 18 h. The mixture is neutralised with NaHCO3 and sat. aq. NaHCO3 solution and then extracted three times with diethyl ether. The combined org. extracts are dried over MgSO4, filtered and concentrated. The crude product is purified by CC on silica gel eluting with heptane:EA 3:2 to give 4-bromo-6-methyl-pyridine-2-carboxylic acid ethyl ester (2.42 g) as a yellow oil; LC-MS: tR=0.86 min, [M+1]+=243.96.
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