tert-Butyl bromoacetate → (S)-tert-Butyl 3-((R)-4-benzyl-2-oxooxazolidine-3-carbonyl)hex-5-enoate

Participants

Reaction Conditions

Reaction Steps

A dry round bottom flask was charged with 1a (3.2 g, 12.34 mmol) and dry THF (123 mL) and then cooled to −78° C. To this solution NaHMDS (1M in THF, 13.57 mL, 13.57 mmol) was added over a period of 10 minutes. To ensure complete enolization, the reaction mixture was stirred for an additional 20 minutes at −78° C. A solution of tert-butyl bromoacetate (2.74 mL, 18.51 mmol) in THF (6 mL) was then introduced to the reaction flask. The solution was stirred for 1 hour at −78° C. and then warmed to −48° C. while still stirring. The reaction was monitored by TLC (˜3 h) and quenched with saturated aqueous NH4Cl. The reaction mixture was concentrated by the removing the THF under reduced pressure. The residue was then diluted with dichloromethane. This solution was washed successively with water and brine, dried over Na2SO4, and concentrated under reduced pressure to give white crystals of 2a (4.27 g, 93%). 1H NMR (500 MHz, CDCl3): δ ppm 7.32-7.37 (m, 2H) 7.27-7.30 (m, 3H) 5.74-5.85 (m, 1H) 5.05-5.13 (m, 2H) 4.63-4.70 (m, 1H) 4.25-4.32 (m, 1H) 4.16 (d, J=4.9 Hz, 2H) 3.34 (dd, J=13.4, 2.7 Hz, 1H) 2.74-2.87 (m, 2H) 2.39-2.52 (m, 2H) 2.19-2.26 (m, 1H) 1.44 (s, 9H); 13C NMR (126 MHz, CDCl3): δ 175.0, 171.1, 153.0, 135.6, 134.4, 129.4, 128.8, 127.1, 117.7, 80.6, 65.8, 55.4, 39.0, 37.5, 36.6, 36.1, 28.0. HRMS calcd for C21H27NO5 (M+H) m/z 374.1967, found 374.1971.

Provenance & Evidence