10242-01-0

1006-94-6

124-38-9

10242-01-0

The general procedure for the synthesis of 5-methoxy-1H-indole-3-carboxylic acid from 5-methoxyindole and carbon dioxide was as follows: lithium tert-butoxide (LiOtBu, 160 mg, 2.00 mmol) and 5-methoxyindole (1a, 23.4 mg, 0.4 mmol) were added to a dry two-necked test tube. The reaction vessel was evacuated under high vacuum and the reaction atmosphere was replaced with a carbon dioxide balloon. Subsequently, N,N-dimethylformamide (DMF, 2 mL) was added and the mixture was stirred at 100 °C for 24 h of reaction. Upon completion of the reaction, the mixture was cooled to room temperature, the reaction was carefully quenched with 2N hydrochloric acid (HCl) solution and extracted with ethyl acetate (EtOAc, 5 times). The organic layers were combined, washed sequentially with water (2 times) and saturated brine (1 time) and dried over anhydrous magnesium sulfate (MgSO4). The dried organic phase was concentrated under reduced pressure and the residue was purified by preparative thin layer chromatography (TLC, unfolding reagent ratio of petroleum ether: acetone = 1:1) to afford the target product 5-methoxy-1H-indole-3-carboxylic acid (2a, 153.0 mg, 95% yield) as a white solid.