NC(N)=[O:3].OO.FC(F)(F)C(OC(=O)C(F)(F)F)=O.[Cl:20][C:21]1[CH:26]=[CH:25][C:24]([S:27]([C:30]2[CH:35]=[CH:34][CH:33]=[CH:32][C:31]=2[F:36])(=[O:29])=[O:28])=[CH:23][N:22]=1.O>ClCCl>[Cl:20][C:21]1[CH:26]=[CH:25][C:24]([S:27]([C:30]2[CH:35]=[CH:34][CH:33]=[CH:32][C:31]=2[F:36])(=[O:29])=[O:28])=[CH:23][N+:22]=1[O-:3]Urea-hydrogen peroxide (0.36 g, 3.83 mmol) was suspended in dichloromethane (3 mL) and trifluoroacetic anhydride (0.77 g, 3.67 mmol) was added to form a clear solution. 2-Chloro-5-[(2-fluorophenyl)sulfonyl]pyridine (Example 1 Steps 1 and 2, 0.5 g, 1.84 mmol) in dichloromethane (1 mL) was added and the reaction stirred at room temperature under nitrogen for 7 hours. The mixture was poured into water and extracted with ethyl acetate. The organic phase was washed with saturated aqueous sodium thiosulfate (×3). The combined aqueous layers were extracted once with ethyl acetate, then the combined organic layers washed again with sodium thiosulfate then with brine, dried over MgSO4 and concentrated in vacuo to give 2-chloro-5-[(2-fluorophenyl)sulfonyl]pyridine 1-oxide as a pale yellow solid (0.53 g, quant.). δH (500 MHz, d6 DMSO): 8.84 (1H, d, J=1.5 Hz), 8.08 (1H, td, J=7.5, 1.5 Hz), 8.03 (1H, d, J=8.6 Hz), 7.87–7.77 (2H, m), 7.51 (1H, q, J=8 Hz), 7.47 (1H, d, J=8.6 Hz); m/z (ES+) 288 [MH+].
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