反应详情

温度

-78 °C

To (4-bromo-2,6-dimethyl-phenyl)-carbamic acid ethyl ester (1t, 1.0 g) dissolved in dry tetrahydrofuran (25 mL) under argon was added isopropylmagnesium chloride (2 M in tetrahydrofuran, 1.9 mL) over 5 minutes and then stirred for 30 minutes. The reaction mixture was cooled to −78° C. and tert-butyllithium (1.7 M in heptane, 4.5 mL) was added dropwise while keeping the internal temperature below −65° C. The temperature of the reaction was raised to −10° C. after complete addition, and then cooled to −78° C. again followed by addition of N,N-dimethylformamide (0.6 mL). The reaction was stirred for 30 minutes at −78° C., 30 minutes at 25° C. and then poured onto crushed ice mixed with acetic acid (25 mL). The mixture was stirred for 30 minutes, extracted with ethyl acetate (3×100 mL), dried over magnesium sulfate, and concentrated in vacuo. The crude product was subjected to flash chromatography to furnish 0.60 g (73% yield) of the title compound as a white solid. LC-MS (m/z) 222 (MH+); tR=2.14, (UV, ELSD) 86%, 99%. 1H NMR (500 MHz, CDCl3): 1.30 (t, 3H), 2.34 (s, 6H), 4.21 (q, 2H), 6.28 (b, 1H), 7.59 (s, 2H), 9.92 (s, 1H).

1. customthe internal temperature below −65° C
2. temperatureThe temperature of the reaction was raised to −10° C.
3. additionafter complete addition
4. temperaturecooled to −78° C.
5. stirringThe reaction was stirred for 30 minutes at −78° C., 30 minutes at 25° C.
6. additionpoured
7. customonto crushed ice
8. stirringThe mixture was stirred for 30 minutes
9. extractionextracted with ethyl acetate (3×100 mL)
10. dry with materialdried over magnesium sulfate
11. concentrationconcentrated in vacuo