Dimethylformamide → 6-Bromo-5-fluoroindole

Temperature

130 °C

A 2 L dry round bottom flask was charged with 1-bromo-2-fluoro-4-methyl-5-nitrobenzene (24.5 g, 0.1 mol, 97%), DMF-DIPA (39 g, 0.22 mol), Et3N (16 mL, 0.11 mol) and dry DMF (100 mL). The mixture was stirred at 130° C. for 2 h. After removal of the volatiles the residue was dissolved in a mixture of toluene (650 mL) and acetic acid (390 mL) followed by addition of iron powder (55 g) and silica gel (50 g). The dark red mixture was heated to 100° C. with vigorous stirring. The dark color disappeared after refluxing for 20 min indicating completion of reaction. The mixture was then cooled to 25° C., diluted with EtOAc and filtered. The cake was washed thoroughly with EtOAc. The combined filtrates were washed with sat. aq. Na2S2O5, sat. aq. NaHCO3, and brine, dried over Na2SO4 and concentrated. The residue was purified on a silica gel column eluting with 5/1 hexanes/CH2Cl2 to provide 6-bromo-5-fluoro-1H-indole as a white crystalline solid (16.2 g, 76%).

1. customA 2 L dry round bottom flask
2. customAfter removal of the volatiles the residue
3. dissolutionwas dissolved in a mixture of toluene (650 mL) and acetic acid (390 mL)
4. additionfollowed by addition of iron powder (55 g) and silica gel (50 g)
5. temperatureThe dark red mixture was heated to 100° C. with vigorous stirring
6. temperatureafter refluxing for 20 min
7. customcompletion of reaction
8. temperatureThe mixture was then cooled to 25° C.
9. filtrationfiltered
10. washThe cake was washed thoroughly with EtOAc
11. washThe combined filtrates were washed with sat. aq. Na2S2O5, sat. aq. NaHCO3, and brine
12. dry with materialdried over Na2SO4
13. concentrationconcentrated
14. customThe residue was purified on a silica gel column
15. washeluting with 5/1 hexanes/CH2Cl2

ORD record

ord-2a99895f24bf45cca43bba21b7c59517

Source dataset

uspto-grants-2014_05

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08735414B2