1-Propanesulfonic acid, 1,1,2,3,3,3-hexafluoro- → Tris-(4-hydroxyphenyl) sulfonium 3,3,3,2,1,1-hexafluoropropane sulfonate

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A solution of 56.8 g (0.08 mol) of tris-(4-butoxyphenyl) sulfonium 3,3,3,2,1,1-hexafluoropropane sulfonate and 1.86 g (0.008 mol) of 3,3,3,2,1,1-hexafluoropropane sulfonic acid in 200 ml of ethanol was refluxed for 8 hours with stirring. After evaporation of the solvent, the obtained crude product of tris-(4-hydroxyphenyl) sulfonium 3,3,3,2,1,1-hexafluoropropane sulfonate (yield about 100%) was dissolved in 160 g of N,N-dimethylformamide and reacted with 55.4 g (0.40 mol) of anhydrous potassium carbonate and 60.3 g (0.40 mol) of t-butyl chloroacetate at 80° C. for 3 hours. The cooled reaction mixture was poured into 700 ml of water and extracted with dichloromethane. The organic phase was washed with water and dried. The solvent was removed. The oily residue was purified by column chromatography on silica gel using a dichloromethane and methanol as the eluent. The white product was collected to yield 31.8 g (yield 45%) of analytically pure tris-(4-t-butoxycarbonylmethoxyphenyl) sulfonium 3,3,3,2,1,1-hexafluoropropane sulfonate. The melting point of the product was 78° C. The 1H-NMR spectrum gave the following signals (CDCl3): δ=1.45 (s, 27H), 4.56 (s, 6H), 5.20-5.56 (d[m], 1H), 7.10-7.13 (d, 6H), 7.55-7.60 (d, 6H).

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