Hydrochloric Acid → Ethyl 5-bromo-1H-indole-3-carboxylate

Trifluoroacetic anhydride (8.5 ml) was added to a solution of 5-bromoindole (10.0 g) in N,N-dimethylformamide (50 ml) at 0° C., and stirred at the same temperature for three hours. After completion of the reaction, water was added to the reaction solution and the precipitated crystalline was collected by filtration. Water (250 ml) and sodium hydroxide (50 g) were added to a solution of the resulting residue in ethanol (50 ml) and the mixture was stirred at 120° C. for eight hours. After completion of the reaction, the reaction solution was cooled to room temperature, concentrated hydrochloric acid was added and the precipitated solid was collected by filtration. To a solution of the resulting residue in ethanol (250 ml), was added concentrated sulfuric acid (5.0 ml) and the mixture was stirred at 90° C. for three hours. Concentrated sulfuric acid (5.0 ml) was further added and stirred at the same temperature for four hours. After completion of the reaction, the reaction solution was cooled to room temperature, and 4N aqueous solution of sodium hydroxide was added until the solution becomes pH 7. Ethanol was evaporated, the precipitated solid was collected and the resulting residue was purified with silica gel column chromatography (n-hexane/ethyl acetate) to give 5-bromo-1H-indole-3-carboxylic acid ethyl ester (5.40 g) as a white solid.

1. additionwas added to the reaction solution
2. filtrationthe precipitated crystalline was collected by filtration
3. additionWater (250 ml) and sodium hydroxide (50 g) were added to a solution of the resulting residue in ethanol (50 ml)
4. stirringthe mixture was stirred at 120° C. for eight hours
5. customAfter completion of the reaction
6. filtrationthe precipitated solid was collected by filtration
7. additionTo a solution of the resulting residue in ethanol (250 ml), was added concentrated sulfuric acid (5.0 ml)
8. stirringthe mixture was stirred at 90° C. for three hours
9. additionConcentrated sulfuric acid (5.0 ml) was further added
10. stirringstirred at the same temperature for four hours
11. customAfter completion of the reaction
12. temperaturethe reaction solution was cooled to room temperature
13. customEthanol was evaporated
14. customthe precipitated solid was collected
15. customthe resulting residue was purified with silica gel column chromatography (n-hexane/ethyl acetate)

ORD record

ord-43c993b1714042a891a2c895d09e90c2

Source dataset

uspto-grants-2015_10

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09150555B2