[Br:1]([O-])(=O)=O.[Na+].[F:6][C:7]([F:21])([F:20])[C:8]1[CH:13]=[CH:12][CH:11]=[CH:10][C:9]=1[CH2:14][C:15]([O:17][CH2:18][CH3:19])=[O:16].S(=O)(O)[O-].[Na+].S(S([O-])=O)([O-])=O.[Na+].[Na+]>O.C(OCC)(=O)C>[Br:1][CH:14]([C:9]1[CH:10]=[CH:11][CH:12]=[CH:13][C:8]=1[C:7]([F:20])([F:21])[F:6])[C:15]([O:17][CH2:18][CH3:19])=[O:16]
585 mg (3.89 mmol) of sodium bromate were initially charged in 2 ml of water, and 300 mg (1.29 mmol) of ethyl 2-(trifluoromethyl)phenylacetate, dissolved in 2.5 ml of ethyl acetate, were added at RT. A solution of 403 mg (3.89 mmol) of sodium bisulfite in 3.8 ml of water was then added slowly. The mixture was stirred at RT for 18 h. 5 ml of 10% strength aqueous sodium dithionite solution were then added. The mixture was extracted with 15 ml of ethyl acetate, and the organic phase was washed in each case once with 5 ml of 10% strength sodium dithionite solution and 5 ml of saturated sodium chloride solution. The organic phase was dried over sodium sulfate, filtered and concentrated under reduced pressure. The crude product was purified by chromatography on silica gel (mobile phase: cyclohexane/ethyl acetate 20:1, then 10:1). This gave 186 mg of a mixture consisting of the title compound and the starting material ethyl 2-(trifluoromethyl)phenylacetate (ratio 16:84 according to GC/MS [Method 20]). This mixture was once more reacted with 362 mg (2.40 mmol) of sodium bromate and 250 mg (2.40 mmol) of sodium bisulfite according to the procedure described above. Work-up gave a mixture of 31% title compound and 69% ethyl 2-(trifluoromethyl)phenylacetate, which was reacted further without any further purification.
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