Acetic Acid → 2-Butyloxirane

Participants

Reaction Conditions

Reaction Steps

(R)-1,2-Epoxyhexane was prepared as reported by Jacobsen and coworkers (Schaus, et al., J. Am. Chem. Soc. 2002, 124, 1307-1315). Ring opening of the optically pure epoxide by vinyl magnesium bromide followed by epoxidation with mCPBA were performed in an analogous manner as 6h to give a 1:1 mixture of diastereomers. The diastereomers were resolved using Jacobsen HKR conditions. The epoxide (2.67 g, 18.5 mmol) was diluted in 2.5 mL THF. To this solution was added (1R,2R)-(−)-1,2-cyclohexanediamino-N,N′-bis(3,5-di-tbutylsalicylidene)cobalt (56.2 mg, 0.93 mmol) and glacial acetic acid (21.2 μL, 0.37 mmol). The solution was cooled to 0° C. and water (183 μL 10.2 mmol) was added dropwise. After stirring at room temperature for 24 hours, THF was removed in vacuo and the residue was distilled under vacuum at 65° C. to afford (R,R)-6b (1.18 g, 13% from racemic 1,2-epoxyhexane, >99:1 syn:anti) as a colorless oil. 1H NMR (δ, CDCl3, 300 MHz) 0.85 (t, 3J=6.9 Hz, 3H), 1.17-1.81 (m, 8H), 2.42-2.49 (m, 1H), 2.47 (d, 3J=4.2 Hz, 1H), 2.72 (t, 3J=4.2 Hz, 1H), 2.99-3.07 (m, 1H), 3.74-3.86 (m, 1H); 13C NMR (δ, CDCl3, 75 MHz) 14.13, 22.75, 27.77, 37.22, 39.84, 46.73, 50.69, 70.38.

Provenance & Evidence