反应详情

温度

-40 °C

To a solution of 2,3-dibromo-5-chloropyridine (60 g, 221 mmol) in THF (500 mL) was added a solution of isopropylmagnesium chloride lithium chloride solution in THF (1.3M, 185 mL) at −40° C. over about 30 min. The solution was stirred for 30 min at −40° C. and DMF (50 mL) was added. The resulting solution was warmed up to room temperature and stirred for 30 min. The reaction was quenched with 1 N HCl (400 mL) and MTBE (200 mL) was added. Organic layer was separated and washed twice with 5% aqueous NaHCO3 (200 mL). The solvent was removed under vacuum at 50° C. The resulting solids (aldehyde intermediate) were dissolved in methanol (400 mL). The solution was cooled to 5° C. under an ice bath. NaBH4 (3.6 g) was added slowly over 30 min while maintaining the reaction temperature below room temperature. The reaction mixture was stirred for another 30 min followed by addition of water (125 mL). The resulting mixture was concentrated under vacuum to approximately 150 ml. Solids precipitated during the concentration. The suspension was stirred vigorously at room temperature for 1 h and solids were collected by filtration. The wet cake was dried in a vacuum oven over night at 60° C. to give 52 (45.6 g, 93%) as a solid. 1H NMR (CDCl3, 400 MHz): δ 8.26 (d, J=2.5 Hz, 1H), 7.88 (d, J=2.5 Hz, 1H), 4.73 (d, J=5.8 Hz, 2H), 2.33 (t, J=11.4 Hz, 1H); 13C NMR (CDCl3, 100 MHz): δ 147.12, 138.48, 138.39, 136.14, 132.06, 62.76.

1. temperatureThe resulting solution was warmed up to room temperature
2. stirringstirred for 30 min
3. customThe reaction was quenched with 1 N HCl (400 mL) and MTBE (200 mL)
4. additionwas added
5. customOrganic layer was separated
6. washwashed twice with 5% aqueous NaHCO3 (200 mL)
7. customThe solvent was removed under vacuum at 50° C
8. dissolutionThe resulting solids (aldehyde intermediate) were dissolved in methanol (400 mL)
9. temperatureThe solution was cooled to 5° C. under an ice bath
10. additionNaBH4 (3.6 g) was added slowly over 30 min
11. temperaturewhile maintaining the reaction temperature below room temperature
12. stirringThe reaction mixture was stirred for another 30 min
13. additionfollowed by addition of water (125 mL)
14. concentrationThe resulting mixture was concentrated under vacuum to approximately 150 ml
15. customSolids precipitated during the concentration
16. stirringThe suspension was stirred vigorously at room temperature for 1 h
17. filtrationsolids were collected by filtration
18. customThe wet cake was dried in a vacuum oven over night at 60° C.