反应详情

温度

-78 °C

1,1-Dimethylethyl carbamate (5 g, 42.7 mmol) was dissolved in tetrahydrofuran (THF) (100 mL) in a 500 mL 3 necks round bottom flask and cooled at −78° C. under nitrogen. n-Butyl lithium (1.6 M in THF, 26.7 mL, 42.7 mmol) and (2E)-2-butenoyl chloride (4.55 mL, 42.7 mmol) were added in slow successive additions as follow: 1) n-Butyl lithium: 13.4 mL and (2E)-2-butenoyl chloride 2.28 mL; 2) n-Butyl lithium:6.8 mL and (2E)-2-butenoyl chloride 1.14 mL; 3) n-Butyl lithium:3.34 mL and (2E)-2-butenoyl chloride 0.57 mL; 4) n-Butyl lithium: 1.67 mL and (2E)-2-butenoyl chloride 0.28 mL (2×). A five to ten minutes waiting time was observed between each double addition, and the final mixture was stirred for an extra 30 minutes period at −78° C. The temperature was kept below −60° C. during the additions. The reaction mixture was then slowly poured into a stirred saturated NaHCO3 aqueous solution (250 mL). The aqueous layer was extracted with AcOEt (2×250 mL). The combined organic phases were washed with brine (150 mL), dried over MgSO4 and concentrated in vacuovacuo. Purification of the residue by flash chromatography on silica gel (gradient:50 to 100% AcOEt in Hexanes) gave 1,1-dimethylethyl (2E)-2-butenoylcarbamate (2.21 g, 11.93 mmol, 28%) as a white solid.

1. waitA five to ten minutes waiting time
2. additionwas observed between each double addition
3. customwas kept below −60° C. during the additions
4. extractionThe aqueous layer was extracted with AcOEt (2×250 mL)
5. washThe combined organic phases were washed with brine (150 mL)
6. dry with materialdried over MgSO4
7. concentrationconcentrated in vacuovacuo
8. customPurification of the residue by flash chromatography on silica gel (gradient:50 to 100% AcOEt in Hexanes)