1011-65-0

141452-01-9

The general procedure for the synthesis of indoline-5-carboxylic acid methyl ester from indole-5-carboxylic acid was as follows: to a 10 mL solution of 1H-indole-5-carboxylic acid methyl ester (1 g, 5.71 mmol) in acetic acid was slowly added sodium cyano-borohydride (1.08 g, 17.18 mmol) at 0 °C, with the addition time being controlled to be within 5 minutes. The reaction mixture was stirred at room temperature for 1 hour. Upon completion of the reaction, water (3 mL) was added and all solvent was evaporated under reduced pressure. The residue was dissolved in ethyl acetate (150 mL) and saturated sodium bicarbonate solution (150 mL) for liquid-liquid separation. The aqueous phase was further extracted with ethyl acetate (3 x 75 mL). All organic phases were combined, washed with saturated saline (150 mL), dried over anhydrous sodium sulfate and filtered, and the filtrate was concentrated under reduced pressure. The crude product was purified by fast column chromatography (eluent: 0-50% hexane solution of ethyl acetate containing 0.1% triethylamine) to afford the target product methyl indoline-5-carboxylate (0.99 g, 99% yield).