反应详情

温度

-5 °C

Ethyl 2-chloro-2-oxoacetate (99 g, 725 mmol) was dissolved in 2-methyltetrahydrofuran (800 ml) and 4-(dimethylamino)-pyridine (1.25 g, 10.0 mmol) was added. The mixture was cooled to −5° C. and a solution of triethylamine (76.2 g, 753 mmol) and (E)-ethyl 3-(dimethylamino)acrylate (106 g, 740 mmol) in 2-methyltetrahydrofuran (70 ml) was added via dropping funnel. The mixture was stirred for 3 h at ca. 0° C. After that, 5% (m/m) aqueous sodium chloride solution (250 mL) was added, the mixture was concentrated in vacuo to remove the 2-methyltetrahydrofuran. Ethyl acetate (800 mL) and 5% (m/m) aqueous sodium chloride solution (250 mL) were added, the organic phase was washed with 5% (m/m) aqueous sodium chloride solution (4×250 mL), the combined aqueous layers reextracted with ethyl acetate (2×300 mL) and the combined organic extracts concentrated in vacuo. The residue was filtered over silica gel (500 g, eluting with ethyl acetate/n-heptane 3:2 (v/v)) and the combined filtrates concentrated in vacuo to afford 146 g crude product as an orange oil. The crude product was dissolved at room temperature in tert-butylmethylether (1 L) and cooled to 1° C. Crystallization started at ca. 13° C. The suspension was filtered and washed with few cold tert-butylmethylether to afford 116.6 g of the title compound as light yellow crystals (66%, purity 99.9% by HPLC). MS (GC-split): m/z=243 [M]+. 1H NMR (CDCl3, 600 MHz); δ 1.26 (t, J=7.1 Hz, 3H), 1.36 (t, J=7.1 Hz, 3H), 3.03 (s, 3H), 3.36 (s, 3H), 4.17 (q, J=7.1 Hz, 2H), 4.30 (q, J=7.1 Hz, 2H), 7.85 (s, 1H). The product was isolated as single isomer.

1. concentrationthe mixture was concentrated in vacuo
2. customto remove the 2-methyltetrahydrofuran
3. additionEthyl acetate (800 mL) and 5% (m/m) aqueous sodium chloride solution (250 mL) were added
4. washthe organic phase was washed with 5% (m/m) aqueous sodium chloride solution (4×250 mL)
5. concentrationthe combined organic extracts concentrated in vacuo
6. filtrationThe residue was filtered over silica gel (500 g, eluting with ethyl acetate/n-heptane 3:2 (v/v))
7. concentrationthe combined filtrates concentrated in vacuo
8. customto afford 146 g crude product as an orange oil
9. temperaturecooled to 1° C
10. customCrystallization
11. customstarted at ca. 13° C
12. filtrationThe suspension was filtered
13. washwashed with few cold tert-butylmethylether