Ethyl 7-chloroindole-2-carboxylate

115050-49-2

43142-64-9

General procedure for the synthesis of ethyl 7-chloro-1H-indole-2-carboxylate from the compound (CAS:115050-49-2): 500 g of polyphosphoric acid and 250 g of phosphoric acid were mixed, stirred and heated up to 90°C. Under stirring conditions, 65 g of phenylhydrazine 2-chlorophenylpyruvate pyruvic acid was slowly added and the temperature of the reaction was controlled to be between 90°C and 100°C. The reaction took about 1 hour. The dosing process takes about 1 hour. After completion of dosing, the reaction temperature was maintained to continue the reaction for 20 minutes and the reaction progress was monitored by TLC. Upon completion of the reaction, 1500 g of ice-water mixture was slowly added to quench the reaction and cooled to room temperature. The precipitate was collected by filtration, washed with water and dried to give a light yellow solid product. Upon drying, 51.3 g of ethyl 7-chloro-1H-indole-2-carboxylate was obtained in 85% yield.