[Br:1][C:2]1[CH:3]=[C:4]([NH2:9])[C:5]([Cl:8])=[N:6][CH:7]=1.C(N(C(C)C)CC)(C)C.[CH3:19][S:20](Cl)(=[O:22])=[O:21].C(=O)([O-])[O-].[K+].[K+].C(O)(=O)CC(CC(O)=O)(C(O)=O)O>ClCCl.O>[Br:1][C:2]1[CH:3]=[C:4]([NH:9][S:20]([CH3:19])(=[O:22])=[O:21])[C:5]([Cl:8])=[N:6][CH:7]=1A solution of 5-bromo-2-chloropyridin-3-amine (1.0 g, 4.8 mmol) and diisopropylethylamine (1.85 mL, 10.6 mmol) in dichloromethane (25 mL) was cooled to 0° C., and then methanesulfonyl chloride (750 uL, 9.6 mmol) was added slowly. The reaction mixture was stirred at 0° C. for 15 min and was then warmed to rt. After stirring for 2 h, water was added, and then the biphasic mixture was partitioned. The organic phase was dried over magnesium sulfate, filtered, and concentrated in vacuo. The residue was then dissolved in dioxane (10 mL) and water (10 mL). Potassium carbonate (2.76 g, 20 mmol) was added, and the reaction mixture was stirred for 15 h at rt. Water was then added to the mixture which was subsequently acidified with aqueous citric acid (10%). The aqueous mixture was extracted twice with ethyl acetate. The combined organic extracts were dried over magnesium sulfate, filtered, and concentrated in vacuo. The residue was purified by flash chromatography (gradient, 100% hexanes to 50% hexanes:50% ethyl acetate) to provide N-(5-bromo-2-chloropyridin-3-yl)methanesulfonamide (520 mg, 1.82 mmol, 38% yield) as a light pink solid. 1H NMR (400 MHz, CDCl3) δ 8.27 (d, 1H), 8.14 (d, 1H), 6.83 (br s, 1H), 3.11 (s, 3H); MS (EI) for C6H6BrClN2O2S: 285, 287, 289 (Br+Cl isotopes, MH+).
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