Trifluoroacetic anhydride → 7-Bromo-1H-indole-3-carboxylic acid

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Reaction Steps

To a solution of 7-bromoindole (10 g, 51.0 mmol) in N,N-dimethylformamide (DMF) (100 cm3) was added trifluoroacetic anhydride (12.5 cm3, 89.6 mmol) over 5 min. The resultant solution was stirred at room temperature for 16 h. The solution was poured onto water (500 cm3) and the precipitate formed was isolated by filtration, washed with water and 4N sodium hydroxide (200 cm3) added. The suspension was heated at reflux for 1.5 h and allowed to cool before washing with diethyl ether (2×250 cm3). The aqueous layer was acidified to pH 1 with 5N hydrochloric acid and the resultant precipitate isolated by filtration, washed with water and dried over phosphorous pentoxide under reduced pressure at 60° C. for 16 h. This afforded the title compound LA) (8.94 g, 73%).

Provenance & Evidence