Cl.[Cl:2][CH2:3][C:4]1[CH:5]=[N:6][CH:7]=[CH:8][C:9]=1[C:10]([F:13])([F:12])[F:11].C([O-])(O)=[O:15].[Na+].ClCC1C=NC=CC=1C(F)(F)F.C1C=C(Cl)C=C(C(OO)=O)C=1>C(Cl)(Cl)Cl>[Cl:2][CH2:3][C:4]1[CH:5]=[N+:6]([O-:15])[CH:7]=[CH:8][C:9]=1[C:10]([F:13])([F:11])[F:12]3-Chloromethyl-4-trifluoromethylpyridine hydrochloride (204 mg, 0.88 mmol) from step 2 above was dissolved in CHCl3 (50 mL) and treated with saturated aqueous NaHCO3. The organic layer was removed, dried (Na2SO4), and concentrated to give the free pyridine. This 3-chloromethyl-4-(trifluoromethyl)pyridine was dissolved in CHCl3 (10 mL) and MCPBA was added (0.19 g of 80% MCPBA by weight; 0.88 mmol). After 29 h, the solution was extracted with saturated aqueous NaHCO3 (10 mL), dried (Na2SO4), filtered, and evaporated under reduced pressure. The residue was purified by pressurized silica gel column chromatography eluting with EtOAc. 3-Chloromethyl-4-trifluoromethylpyridine-N-oxide was obtained as a solid (TLC: Rf = 0.35 (EtOAc); FAB MS m/z 212 (M+ +H)).
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