A solution of 5-chloro-N-[(1S,2R)-4,4,4-trifluoro-1-hydroxymethyl)-2-methylbutyl]thiophene-2-sulfonamide (prepared as in Example 1, 3.0 g, 8.53 mmol) in CH2Cl2 saturated with water (30 mL) was stirred under nitrogen at 0° C. Dess-Martin periodinane reagent (7.59 g, 17.90 mmol) was added in one portion. The resulting suspension was stirred at 25° C., monitoring the progress of reaction by TLC analysis (1:2 EtOAc/hexane). As the rate of conversion of the starting material slowed, additional 2 mL portions of CH2Cl2 saturated with water were added (three portions over 15 min). After 19 h at 25° C., the reaction was complete by TLC. The solution was diluted with Et2O (50 mL) and a solution of sodium thiosulfate, Na2S2O3 (93.83 mmol, 14.8 g, 11 eq) in 80% saturated aqueous sodium bicarbonate solution (50 mL) was added. The mixture was stirred rapidly for 10 min until both phases were clear. The layers were separated and the aqueous phase was extracted with ether (30 mL). The combined organic layers were washed sequentially with saturated aqueous sodium bicarbonate (10 mL) and brine (15 mL), then dried over MgSO4, filtered and concentrated to obtain a crude oil (2.67 g). The crude product was purified by the Biotage Flash™ 60 chromatography system, eluent: 1:6 EtOAc-hexanes, to afford 5-chloro-N-[(1S,2R)-4,4,4-trifluoro-1-formyl-2-methylbutyl]thiophene-2-sulfonamide as a colorless oil (2.65 g, 88.93%). Mass Spectrum (+ESI): 350 (M+H)+.
