[F:1][C:2]([F:15])([F:14])[C:3]1[N:8]=[C:7]([C:9]([OH:11])=[O:10])[CH:6]=[C:5]([CH:12]=C)[CH:4]=1.I([O-])(=O)(=O)=[O:17].[Na+].S([O-])([O-])(=O)=S.[Na+].[Na+].Cl>O1CCOCC1.O.[Os](=O)(=O)(=O)=O>[CH:12]([C:5]1[CH:4]=[C:3]([C:2]([F:15])([F:14])[F:1])[N:8]=[C:7]([C:9]([OH:11])=[O:10])[CH:6]=1)=[O:17]
6-(Trifluoromethyl)-4-vinylpyridine-2-carboxylic acid (0.30 g, 0.69 mmol, the crude product from Step A) was dissolved in 1,4-dioxane (20. mL) and water (5.0 mL), then sodium periodate (0.44 g, 2.1 mmol, Aldrich) was added, followed by 4 wt % osmium tetraoxide in water (0.152 mL, 0.0240 mmol, Aldrich). The reaction was stirred overnight. Sodium thiosulfate solution was added and the mixture was stirred for 30 minutes. 1N HCl was added to adjust the pH to between 4 and 5, and the product was extracted with ten portions of 10% isopropanol in CHCl3. The combined extracts were dried over sodium sulfate, filtered and concentrated. Flash chromatography on silica gel, eluting with a gradient from 0-10% MeOH in DCM afforded a partially purified product (94 mg, 20% yield over Steps A & B). 1H NMR (300 MHz, CDCl3) δ 10.25 (s, 1H), 8.83 (d, J=0.8 Hz, 1H), 8.38 (d, J=1.3 Hz, 1H).
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