Synthesis
Methyl 4-methoxy-2-indolecarboxylate (4 g, 19.49 mmol, 1 eq) was added to an aqueous solution of sodium hydroxide (2M, 98 mL, 0.20 mmol, 10 eq). The suspension was stirred and heated until the reaction mixture was uniform, and then the mixture was refluxed for 30 minutes with heating. The mixture solution was acidified, and the resulting precipitate was extracted three times with ethyl acetate (100 mL). The extracts were combined, washed with water, dried over magnesium sulfate, and concentrated to give a white solid of 4-methoxy-1H-indole-2-carboxylic acid (3.71 g, yield 99 per cent).
