Cl[C:2]1[CH:7]=[C:6]([C:8]([F:11])([F:10])[F:9])[CH:5]=[C:4]([C:12]([F:15])([F:14])[F:13])[N:3]=1.[S:16]([O-:19])([OH:18])=[O:17].[Na+:20].C(O)C>O>[F:9][C:8]([F:11])([F:10])[C:6]1[CH:5]=[C:4]([C:12]([F:15])([F:14])[F:13])[N:3]=[C:2]([S:16]([O-:19])(=[O:18])=[O:17])[CH:7]=1.[Na+:20]A mixture of 2-chloro-4,6-bis(trifluoromethyl)pyridine (2.50 g, 10 mmol), sodium hydrogen sulfite (4.2 g, 40 mmol), ethanol (40 ml) and water (40 ml) was heated under reflux for 96.5 hours. The reaction mixture was evaporated to dryness under reduced pressure. To the residue, conc. hydrochloric acid was added and the mixture was again evaporated to dryness. The residued was extracted with methanol, and a methanol phase was filtered. The filtrate was evaporated to dryness under reduced pressure to obtain sodium 4,6-bis(trifluoromethyl)pyridine-2-sulfonate (2.11 g). Yield, 66%.
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