[C:1]1([CH3:11])[CH:6]=CC(S(Cl)(=O)=O)=C[CH:2]=1.[Br:12][C:13]1(C(O)=O)[CH:18]=[CH:17][CH:16]=[CH:15][NH:14]1.N1C=CC=CC=1.[C:28](=[O:31])(O)[O-:29].[Na+]>C(O)(C)(C)C>[Br:12][C:13]1[N:14]=[C:15]([C:28]([O:29][C:1]([CH3:11])([CH3:6])[CH3:2])=[O:31])[CH:16]=[CH:17][CH:18]=1p-Toluenesulfonyl chloride (9.0 g, 47.2 mmol) was added portionwise to a mixture of 2-bromo-picolinic acid (4.02 g, 19.9 mmol) in tert-butanol (36 mL) and pyridine (10.8 mL, 134 mmol) at 0° C. and the mixture was stirred at rt for 14 hours. An aqueous solution of sodium bicarbonate was slowly added. The precipitate was filtered, washed with water and dried in vacuo to provide 4.04 g (79%) of the desired product tert-butyl 6-bromopicolinate (25A): 1H NMR (300 MHz, CDCl3) δ 7.97 (1H, dd), 7.64 (2H, m), 1.62 (9H, s).
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