[C:1]([O:10][CH3:11])(=[O:9])[C:2]1[C:3](=[CH:5][CH:6]=[CH:7][CH:8]=1)[SH:4].[F:12][C:13]1[N:18]=[C:17]([F:19])[C:16]([F:20])=[C:15](F)[C:14]=1[F:22].C(=O)([O-])[O-].[Cs+].[Cs+].[OH-].[K+]>CN(C=O)C.C(OCC)(=O)C>[CH3:11][O:10][C:1]([C:2]1[CH:8]=[CH:7][CH:6]=[CH:5][C:3]=1[S:4][C:15]1[C:14]([F:22])=[C:13]([F:12])[N:18]=[C:17]([F:19])[C:16]=1[F:20])=[O:9]
To a solution of methyl thiosalicylate (1.0 g, 5.9 mmol) in dry DMF (15 mL) at 0° C. was added pentafluoropyridine (1.2 g, 7.1 mmol) and cesium carbonate (2.5 g, 7.7 mmol). The resultant mixture was stirred at ambient temperature for 5 hours then poured into 100 mL of 0.5 M aqueous KOH solution and 100 mL of ethyl acetate. The aqueous layer was separated and extracted with another 100 mL of ethyl acetate. The combined organic extracts were washed with 0.5 M aqueous KOH solution (100 mL) then brine (100 mL), dried over MgSO4, filtered, and concentrated in vacuo to afford 1.8 g (98% yield) of 4-(2-methoxycarbonylphenyl)thio-2,3,5,6-tetrafluoropyridine as a crystalline solid, NMR (CDCl3) 8.1 (dd, 1), 7.4 (m, 1), 7.4 (tt, 1), 7.0 (d, 1), 4.0 (s, 3) ppm.
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