[Br:1][C:2]1[CH:7]=[CH:6][C:5]([CH3:8])=[CH:4][N:3]=1.C1C=C(Cl)C=C(C(OO)=[O:17])C=1.C([O-])([O-])=O.[K+].[K+]>ClCCl>[Br:1][C:2]1[CH:7]=[CH:6][C:5]([CH3:8])=[CH:4][N+:3]=1[O-:17]To a solution of 2-bromo-5-methylpyridine (4 g, 2.3 mmol) in dichloromethane (500 mL) was added m-CPBA (52 g, 304 mmol) at 0° C. The reaction mixture was stirred at room temperature for 20 hours and the then the pH was adjusted to about 9 with a saturated solution of K2CO3. The organic layers were separated and concentrated to give a residue which was purified by flash silica chromatography eluted with petroleum ether/ethyl acetate (1:1) to give 2-bromo-5-methylpyridine 1-oxide (33 g; 75%). 1H NMR (CDCL3): δ ppm 8.25 (s, 1H), 8.75 (d, 1H, J=8.4 Hz), 6.95-6.94 (m, 1H), 2.30 (s, 3H).
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