[Br:1][C:2]1[CH:3]=[C:4]([CH:8]([OH:14])[C:9]([N:11]([CH3:13])[CH3:12])=[O:10])[CH:5]=[N:6][CH:7]=1.C1C=C(Cl)C=C(C(OO)=[O:23])C=1.C(O)(=O)C1C=CC=CC=1>C(Cl)Cl>[Br:1][C:2]1[CH:3]=[C:4]([CH:8]([OH:14])[C:9]([N+:11]([O-:23])([CH3:12])[CH3:13])=[O:10])[CH:5]=[N:6][CH:7]=1A solution of 2-(5-bromo-pyridin-3-yl)-2-hydroxy-N,N-dimethyl-acetamide (100 mg, 0.387 mmol) in DCM (3.0 mL) was cooled in an ice water bath and treated with mCPBA (100.3 mg, 0.581 mmol). After stirring at room temperature for 4 h, the mixture was cooled and additional mCPBA was added (66.7 mg, 1 eq.). After stirring 18 h at room temperature, another 0.3 eq of mCPBA was added (13.3 mg). Finally after 4 h, the reaction was quenched by addition of 38% aqueous sodium bisulfite (100 uL) and the mixture was dried over Na2SO4. After filtration, MP—CO3 (1.74 mmol) was added to scavenge the benzoic acid by-product. After 5 d (3 hours is sufficient), the mixture was filtered and the resin was rinsed with 10% MeOH in DCM. The product was concentrated in vacuo to afford 2-(5-bromo-pyridin-3-yl)-2-hydroxy-N,N-dimethyl-acetamide N-oxide (97.0 mg, 91.7%). MS: m/z 275 (M+H+).
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