反应详情

The purified n-butyl ketene dimer 2a, (5.1 mmol, 1.0 g) was dissolved in 40 mL dichloromethane (0.1 M) and transferred to a Parr bomb apparatus under a N.sub.2 atmosphere using an additional 10 mL dichloromethane as wash solvent. Pd/C (107 mg, 1 mol %, 5 wt %) was then added at one time under N.sub.2 atmosphere. The Parr bomb was then subjected to three consecutive evacuation-saturation cycles of hydrogen gas and then pressurized to 30 psi hydrogen gas pressure. Hydrogenation with shaking (Parr shaker) was continued for 30 min at this pressure and then the heterogeneous slurry was vacuum filtered through a plug of Celite, and concentrated yielding a colorless oil. Flash chromatography with gradient elution (5→15% diethyl ether/hexanes; 2.5×35.0×5 cm pad) gave 3-butyl-4-pentyl-oxetan-2-one (3a, 897 mg, 90%) as a colorless oil (>96% ee, chiral GC): Rf 0.47 (15% Et2O:hexanes ); IR (thin film) 1824 cm−1; 1H NMR (300 MHz, CDCl.sub.3) δ 4.54 (ddd, J=2.1, 3.6, 5.7 Hz, 1H), 3.59 (ddd, J=4.5, 5.4, 8.4 Hz, 1H), 1.46-1.84(m,6H), 1.31-1.44 (m, 8H), 0.88-0.94 (m, 6H); 13C NMR (500 MHz, CDCl3) δ 173.1, 76.5, 53.3, 32.2, 30.9, 30.5, 26.0, 24.4, 23.2, 23.2, 14.7, 14.5; ESI LRMS Calcd. for C12H22O2 [M+Li]: 205: Found:205.

1. washas wash solvent
2. additionPd/C (107 mg, 1 mol %, 5 wt %) was then added at one time under N.sub
3. filtrationfiltered through a plug of Celite
4. concentrationconcentrated
5. customyielding a colorless oil
6. washFlash chromatography with gradient elution (5→15% diethyl ether/hexanes; 2.5×35.0×5 cm pad)