1,3-Dichloro-5,5-dimethylhydantoin → 1,1-Dimethylethyl N-[(1S)-2-hydroxy-1-[3-(trifluoromethyl)phenyl]ethyl]carbamate

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Reaction Steps

A 500 mL round-bottomed flask is charged with tert-butyl carbamate (5.42 g, 46.0 mmol) and n-PrOH (48 mL). To this stirred solution is added freshly prepared aqueous solution of NaOH (1.84 g, 46.0 mmol in 75 mL of H2O), followed by 1,3-dichloro-5,5-dimethylhydantoin (4.54 g, 23.0 mmol). After 5 min a solution of (DHQ)2PHAL (584 mg, 0.75 mmol, 5 mol %) in n-PrOH (42 mL) is added. 3-Trifluoromethylstyrene (2.58 g, 15.0 mmol, dissolved in 60 mL of n-PrOH) is then added, followed by K2OsO2(OH)4 (221 mg, 0.6 mmol, 4 mol %). The resulting solution is stirred at rt for 2 h. The reaction mixture is then cooled in an ice-bath, and the reaction is quenched by the addition of sodium sulfite (4.41 g, 35.0 mmol) and stirred for 1 h. Evaporation to remove most of n-PrOH, the aqueous solution is extracted with ethyl acetate (4×100 mL). The combined organic phases were washed with water (50 mL), brine (50 mL), dried over anhydrous Na2SO4, and concentrated and then purified on silica gel (eluent: 0-33% ethyl acetate in hexane) to give tert-butyl (S)-1-[3-(trifluoromethyl)phenyl]-2-hydroxyethylcarbamate (2.42 g, 53%) as a colorless oil. HPLC-MS calculated for C9H11F3NO (M-Boc+H+) 206.07, found 206.10.

Provenance & Evidence