Pentanoic Acid → HCID 68809240, compound

Participants

Reaction Steps

To a stirred solution of pentanoic acid (5.98 g, 58.6 mmol) in CH2Cl2 (100 mL) and 10 drops DMF was added oxalyl chloride (5.64 mL, 64.4 mmol) dropwise over 5 min and the solution stirred for 2.75 h, at which time all bubbling subsided. The solution was concentrated in vacuo. In a separate flask, to a cold (−78° C.), stirred solution of (S)-4-isopropyloxazolidin-2-one (7.56 g, 58.6 mmol) in THF (280 mL) was added n-BuLi (2.5M in hexane, 23.42 mL, 58.6 mmol) dropwise via addition funnel over 20 min (temperature never exceeded −68° C.). After stirring 10 min, the above acid chloride dissolved in THF (50 mL) was added via addition funnel over 25 min. After the addition was complete, the reaction mixture was allowed to warm to room temperature as bath warmed and stirred overnight. The reaction was quenched with water and extracted with EtOAc (2×). The combined organic layers were washed with brine, dried (Na2SO4), filtered and concentrated to an amber oil. The residue was purified by flash chromatography (Teledyne ISCO CombiFlash Rf, 0% to 60% solvent A/B=hex/EtOAc, REDISEP® SiO2 120 g, applied as a DCM solution) to give Preparation 4A (6.51 g, 52%) as a colorless oil: 1H NMR (400 MHz, chloroform-d) δ ppm 4.44 (1H, ddd, J=8.16, 3.51, 3.39 Hz), 4.27 (1H, t, J=9.00 Hz), 4.21 (1H, dd, J=9.00, 3.01 Hz), 2.99 (1H, ddd, J=16.60, 8.50, 6.50 Hz), 2.86 (1H, ddd, J=16.60, 8.50, 6.78 Hz), 2.31-2.44 (1H, m), 1.56-1.72 (2H, m), 1.39 (2H, sxt, J=7.43 Hz), 0.94 (3H, t, J=7.28 Hz), 0.92 (3H, d, J=7.03 Hz), 0.88 (3H, d, J=6.78 Hz); HPLC: RT=2.497 min (CHROMOLITH® SpeedROD 4.6×50 mm (4 min grad) eluting with MeOH/H2O/0.1% TFA, 4 mL/min, monitoring at 220 nm).

Provenance & Evidence