反应详情

温度

75 °C

To a mixture consisting of (R)-5-hydroxymethyl-2-pyrrolidinone (20 g, 174 mmol) in 2,2-dimethoxypropane (1.4 L, 11.400 mmol) was added camphorsulfonic acid (1.0 g, 4.3 mmol). The stirring mixture was heated to 75° C. for 20 hours. The reaction mixture was treated with a saturated aqueous solution of sodium bicarbonate, diluted with water, and extracted with ethyl acetate. The combined organic phase was washed with a saturated aqueous solution of sodium chloride, dried over sodium sulfate, filtered, and concentrated. The residue was purified by silica gel chromatography. Elution with methanol-dichloromethane (1:70 v/v) afforded the title compound as a white solid (21.2 g, 78%); TLC Rf 0.6 (solvent system: 25:75 v/v ethyl acetate-hexane); MS (ESI+) m/z 156.1 (M+H)+, 178.1 (M+Na)+; 1H-NMR (CDCl3) δ 4.3-4.2 (m, 1H), 4.1 (dd, 1H), 3.5 (t, 1H), 2.9-2.7 (m, 1H), 2.6-2.5 (m, 1H), 2.2-2.1 (m, 1H), 1.9-1.7 (m, 1H), 1.7 (s, 3H), 1.5 (s, 3H).

1. extractionextracted with ethyl acetate
2. washThe combined organic phase was washed with a saturated aqueous solution of sodium chloride
3. dry with materialdried over sodium sulfate
4. filtrationfiltered
5. concentrationconcentrated
6. customThe residue was purified by silica gel chromatography
7. washElution with methanol-dichloromethane (1:70 v/v)