反应详情

温度

-78 °C

To a mixture of dimethyl 1-(2-chloroethyl)cyclohexane-1,4-dicarboxylate (116 g, 0.44 mol) and hexamethylphosphoramide (317 mL, 1.7 mol) in anhydrous THF (800 mL) was added freshly prepared lithium diisopropylamide (preparation described above) over 30 min at −40° C. The mixture was stirred for 2 h at −78° C. and then stirred overnight allowing warming to room temperature. To the reaction mixture was added saturated aqueous ammonium chloride solution (200 mL) and the mixture was stirred for 10 min. The volatile solvents were removed by evaporation under reduced pressure. The aqueous layer was extracted with ethyl acetate (3×200 mL) and the combined extracts were washed with brine (300 mL×2) and dried over sodium sulfate. Concentration under reduced pressure gave crude product, which was purified by silica gel column chromatography (10% ethyl acetate in petroleum ether) to afford the title compound (58.0 g, 0.25 mol, yield 50% over two steps). 1H NMR (400 MHz, CDCl3): δ ppm 3.65 (s, 6H), 1.81 (s. 12H).

1. stirringstirred overnight
2. temperatureallowing warming to room temperature
3. stirringthe mixture was stirred for 10 min
4. customThe volatile solvents were removed by evaporation under reduced pressure
5. extractionThe aqueous layer was extracted with ethyl acetate (3×200 mL)
6. washthe combined extracts were washed with brine (300 mL×2)
7. dry with materialdried over sodium sulfate
8. concentrationConcentration under reduced pressure
9. customgave crude product, which
10. customwas purified by silica gel column chromatography (10% ethyl acetate in petroleum ether)