General procedure for the synthesis of 5-bromo-1H-indole-7-carboxylic acid from 5-bromo-1H-indole-7-carboxylic acid: 5-bromo-1H-indole-7-carboxylic acid (10.0 g, 42 mmol) was dissolved in dichloromethane (100 mL) at room temperature, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC, 9.66 g, 50.4 mmol) was added sequentially. 50.4 mmol), 1-hydroxybenzotriazole (HOBt, 6.81 g, 50.4 mmol) and a methanol solution of ammonia (2.0 M, 84 mL, 168 mmol). The reaction mixture was stirred at room temperature for 16 hours. After completion of the reaction, the solvent was removed by evaporation and the residue was extracted by partitioning with ethyl acetate (100 mL) and water (100 mL). The aqueous layer was then extracted twice with ethyl acetate (100 mL x 2), and all organic phases were combined, dried with anhydrous magnesium sulfate, and concentrated to give the crude product 5-bromo-1H-indole-7-carboxamide (10 g, 98% yield). The crude product did not require further purification and could be used directly in the subsequent reaction.LC/MS analysis: m/z 240.0 ([M+H]+), retention time 1.95 min.
