93247-78-0

67-56-1

1670-83-3

93247-78-0

To a solution of 1H-indole-7-carboxylic acid (20 g, 124 mmol, 1.0 eq.) in methanol (700 ml) was slowly added concentrated sulfuric acid (1.2 g, 12 mmol, 0.1 eq.), the temperature of the reaction system was maintained at 0 °C and stirring was continued. The reaction mixture was heated to reflux and maintained for 20 hours. After completion of the reaction, methanol was evaporated under reduced pressure using a rotary evaporator. The residue was dissolved in ethyl acetate and the organic phase was washed sequentially with saturated sodium carbonate solution and brine. The organic layer was dried over anhydrous sodium sulfate and filtered, and the filtrate was concentrated under reduced pressure to give Intermediate 1 (16.3 g, 75% yield) as a yellow solid.