(R)-4-Benzyl-2-oxazolidinone → (R)-4-Benzyl-3-pent-4-enoyloxazolidin-2-one

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A solution of (R)-4-benzyl-2-oxazolidinone (2 g, 0.011 mmol) in dry THF (33 mL) was cooled to −78° C. To this solution n-butyllithium (1.6 M in hexanes, 6.87 mL, 0.011 mmol) was added over a ten-minute period. Following this addition, 4-pentenoyl chloride (1.32 mL, 0.012 mmol) was added in a single portion. The reaction mixture was stirred under argon at −78° C. for 30 minutes and then warmed to room temperature. The reaction progress was monitored by TLC (˜1 h). The reaction mixture was quenched with saturated aqueous ammonium chloride (60 mL) and the product was extracted with dichloromethane (2×80 mL). The combined organic layers were washed successively with 1 N sodium hydroxide and brine, dried over Na2SO4, and filtered. The solution was concentrated in vacuo and the residue was cooled at 4° C. overnight. The resulting solid was triturated using cold hexanes and dried to give a white solid, 1a (2.838 g, 99%). 1H NMR (CDCl3, 500 MHz): δ 7.33-7.37 (m, 1H), 7.28-7.32 (m, 1H), 7.20-7.24 (m, 1H), 5.84-5.96 (m, 1H), 5.13 (dd, J=17.1, 1.5 Hz, 1H), 5.05 (dd, J=10.3, 1.0 Hz, 1H), 4.69 (ddd, 1H), 4.15-4.25 (m, 1H), 3.31 (dd, J=13.2, 3.4 Hz, 1H), 2.99-3.16 (m, 1H), 2.77 (dd, J=13.2, 9.8 Hz, 1H), 2.44-2.51 ppm (m, 1H). 13C NMR (126 MHz, CDCl3): δ 172.8, 136.9, 135.5, 129.6, 129.2, 127.6, 116.0, 110.0, 66.4, 55.4, 38.2, 35.0, 28.4. HRMS calcd for C15H17NO3 (M+H) m/z 260.1286, found 260.1277.

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