Dimethyl Sulfoxide → (S)-Tert-butyl 2,2-dimethyl-4-(2-oxoethyl)oxazolidine-3-carboxylate

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Reaction Conditions

Reaction Steps

(S)-4-(2-Hydroxy-ethyl)-2,2-dimethyl-oxazolidine-3-carboxylic acid t-butyl ester was prepared according to the literature procedure (J. Org. Chem. 2001, 66, 206-215). A solution of dimethylsulfoxide (3.5 mL) in dichloromethane (15 mL) was added dropwise to a cooled solution (−78° C.) of oxalyl chloride (2M in dichloromethane, 13 mL) in dichloromethane (40 mL). The solution was stirred at −60° C. for 15 min before the slow addition of (S)-4-(2-hydroxy-ethyl)-2,2-dimethyl-oxazolidine-3-carboxylic acid t-butyl ester (4.5 g, 18.37 mmol) in dichloromethane (20 mL). The mixture was stirred at −60° C. for 30 min and triethylamine (13 mL) was added. After stirring for 30 min, the cooling bath was removed and the mixture was stirred for 1 h at room temperature. The mixture was extracted with dichloromethane and water. The organic layer was dried over sodium sulfate. Solvents were evaporated to give (S)-2,2-dimethyl-4-(2-oxo-ethyl)-oxazolidine-3-carboxylic acid t-butyl ester (4.50 g, 100%) as a colorless oil: 1H NMR (300 MHz, CDCl3) δ ppm 1.42-1.52 (m, 12H), 1.51, 1.63 (2×s, 3H), 2.50-3.16 (m, 2H), 3.73 (d, J=9.1 Hz, 1H), 3.99-4.16 (m, 1H), 4.22-4.44 (m, 1H), 9.79 (s, 1H).

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