3-Cyclopentylpropionyl chloride → (R)-3-(3-Cyclopentyl-1-oxopropyl)-(1-phenylmethyl)-2-oxazolidinone

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A dry round bottom flask was charged with of (R)-4-(phenylmethyl)-2-oxazolidinone (1, 17.7 g, 0.100 mol). Anhydrous tetrahydrofuran (300 mL) was then added, and the solution was cooled to −78° C. A solution of butyllithium (42.0 mL, 0.105 mol, 2.50 M in hexane) was added to the reaction flask over a 10-min period. After a few minutes, 3-Cyclopentylpropionyl chloride (16.8 mL, 0.110 mol) was added. The resulting solution was stirred for 30 min at −78° C., then allowed to warm to ambient temperature over a 30-min period. Excess 3-cyclopentylpropionyl chloride was quenched by the addition of 60 mL of saturated aqueous ammonium chloride. The bulk of the tetrahydrofuran and hexane was removed on a rotary evaporator, and the slurry was extricated with two 80 mL portion of dichloromethane. The combined organic layers were washed with 75 mL of 1 M sodium hydroxide and 75 mL of brine, dried over anhydrous magnesium sulfate, and filtered. The solvent was removed under reduced pressure. The residue was triturated with hexane to provide 16.5 g of desired product 2 as a white solid. 1H NMR (300 MHz, CDCl3) δ 7.18-7.40 (5 H, m), 4.67 (1 H, m), 4.12-4.22 (2 H, m), 3.30 (1 H, dd, J=13.4, 3.1 Hz), 2.84-3.06 (2 H, m), 2.76 (1 H, dd, J=13.4, 9.6 Hz), 1.42-1.96 (9 H, m), 1.15 (2 H, br, m).

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