In a 250mL three-necked flask, add 80mL of ethanol and 7.2g (40mmol) of 6-bromo-2-indolecarboxylic acid, slowly drop 1.0mL of concentrated sulfuric acid at room temperature and reflux for 30h (TLC tracking). After the reaction, concentrate to 30mL and pour into 60mL of water, extract twice with 20mL of ether, wash the ether layer once with 5% sodium carbonate solution, and then wash with water until neutral, dry with anhydrous magnesium sulfate, and evaporate the ether to obtain 7.7g of yellow to brown powder Ethyl 6-bromoindole-2-carboxylate, with a yield of 92.3%.
