A solution of 200 mg (0.37 mmol) of trans benzyl-N-[4-(2,2,2-trifluoro-1-triethylsilanyloxy-1-trifluoromethyl-ethyl)-cyclohexyl]-sulfonamide (example 29.1) in 2 mL of THF was cooled to −78° C. and treated dropwise with a 0.4 mL of a 1M lithium-bis-(trimethylsilyl)amide-solution in THF. The mixture was warmed to −40° C., treated with 609 mg (2.6 mmol) of trifluoro-methanesulfonic acid 2,2,2-trifluoro-ethyl ester and allowed to reach RT. After 4 hours of refluxing, the mixture was cooled to RT and distributed between a saturated aqueous solution of NH4Cl and Et2O. The combined organic phases were dried over Na2SO4 and the solvent was evaporated. Chromatography on silica gel with heptane/EtOAc 9:1 gave 140 mg (61%) of trans benzyl-N-(2,2,2-trifluoro-ethyl)-N-[4-(2,2,2-trifluoro-1-triethylsilanyloxy-1-trifluoromethyl-ethyl)-cyclohexyl]-sulfonamide as a light yellow oil, MS: 614 (M−H)−.
