Water → (S)-4-(2-methanesulfonyloxy-ethyl)-2,2-dimethyl-oxazolidine-3-carboxylic acid tert-butyl ester

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Reaction Steps

To a stirred solution of tert-butyl (S)-4-(2-hydroxyethyl)-2,2-dimethyl-oxazolidine-3-carboxylate (1.0 g) at 0° C. (ice cooling) in dichloromethane (25 ml) under an argon atmosphere were added N-ethyldiisopropylamine (3.5 ml) and methanesulfonyl chloride (0.56 g). The mixture was stirred at 0° C. for 2.5 hours Water was added and the mixture was extracted 3 times with dichloromethane. The combined organic layers were dried (MgSO4) and evaporated to yield crude (S)-4-(2-methanesulfonyloxy-ethyl)-2,2-dimethyl-oxazolidine-3-carboxylic acid tert-butyl ester. To a stirred solution of this compound (1.4 g) at room temperature in tetrahydrofuran (15 ml) under an argon atmosphere were added 4-fluorothiophenol (1.11 g) and triethylamine (0.88 g). The mixture was stirred at room temperature overnight. The solvent was evaporated and the residue was purified by column chromatography (SiO2; heptane/EtOAc=4:1) to give (S)-4-[2-(4-fluoro-phenylsulfanyl)-ethyl]-2,2-dimethyl-oxazolidine-3-carboxylic acid tert-butyl ester (1.0 g) as a colourless oil which was used for the next step.

Provenance & Evidence