反应详情

To a solution of freshly-prepared LDA (33.9 mmol) in anhyd THF (100 mL) at −78° C. was added a solution of 1,2-dibromo-4-fluorobenzene (4 mL, 32.3 mmol) in THF (8 mL), dropwise at such a rate that the internal temperature remained <−70° C. The mixture was stirred 30 min and iodine (9.02 g, 35.5 mmol) was added in one portion. The mixture was stirred 30 min, quenched by addition of 10% Na2S2O3, and removed from the cooling bath. Upon warming the mixture was poured into water and extracted with EtOAc (×3). Combined organics were washed (water, brine), dried over Na2SO4 and concentrated in vacuo. The residue was eluted from a pad of silica (hexanes→2% EtOAc/hexanes) and recrystallized from MeOH-water affording 1,2-dibromo-4-fluoro-3-iodobenzene (8.59 g, 70% yield) as a white solid: 1H NMR (400 MHz, CDCl3) δ 7.64 (dd, J=8.8, 5.5 Hz, 1H), 6.93 (dd, J=8.8, 7.0 Hz, 1H); MS (GCMS EI) m/z 378 ([M]+, Br isotopes, 56%), 380 ([M]+, Br isotopes, 100%), 382 ([M]+, Br isotopes, 51%).

1. customremained <−70° C
2. stirringThe mixture was stirred 30 min
3. customquenched by addition of 10% Na2S2O3
4. customremoved from the cooling bath
5. temperatureUpon warming the mixture
6. additionwas poured into water
7. extractionextracted with EtOAc (×3)
8. washCombined organics were washed (water, brine)
9. dry with materialdried over Na2SO4
10. concentrationconcentrated in vacuo
11. washThe residue was eluted from a pad of silica (hexanes→2% EtOAc/hexanes)
12. customrecrystallized from MeOH-water