反应详情

温度

-78 °C

To a solution of 5-bromo-2-methylpyridine (1.25 g, 7.2 mmol) in anhydrous THF (15 mL) at −40° C. under an argon atmosphere, lithium dibutyl(isopropyl)magnesate (5.2 mL, 0.7 M, 3.6 mmol) was added. The stirring was continued at the same temperature for 1 h. The resulting mixture was cannulated into a solution of 8 (1.5 g, 5.5 mmol) in THF (20 mL) at −78° C. The solution was maintained at −78° C. for 1 h, and then quenched with sat. aqueous NH4Cl and allowed to warm to room temperature. The organic layer was separated and then the aqueous layer was extracted with ethyl acetate (2×20 mL). The combined organic layer was washed with water, dried over Na2SO4, filtered, and evaporated under reduced pressure to give the crude product. The crude compound was purified by chromatography on silica gel to obtain the desired compound 9a (0.7 g, 42%). 1H NMR (CDCl3): δ 1.49 (s, 9H), 1.68-1.87 (m, 4H), 2.63 (s, 3H), 3.35 (m, 1H), 4.18 (br, 2H), 7.28 (d, J=8.4 Hz, 1H), 8.11 (dd, J=8.4, 2.1 Hz, 1H), 9.04 (d, J=2.1 Hz, 1H).

1. customquenched with sat. aqueous NH4Cl
2. temperatureto warm to room temperature
3. customThe organic layer was separated
4. extractionthe aqueous layer was extracted with ethyl acetate (2×20 mL)
5. washThe combined organic layer was washed with water
6. dry with materialdried over Na2SO4
7. filtrationfiltered
8. customevaporated under reduced pressure
9. customto give the crude product
10. customThe crude compound was purified by chromatography on silica gel