Citric Acid → 4,6-dicyano-1H-indole-2-carboxylic acid

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Reaction Steps

To a stirred solution of ethyl 4,6-dicyano-1H-indole-2-carboxylate (I-2a: 500 mg, 2.09 mmol) in ethanol (10 mL) was added LiOHH2O (176 mg, 4.18 mmol) and heated to reflux for 6 h. Ethanol was evaporated under reduced pressure and the residue was washed with diethyl ether. The solid formed was dissolved in water (20 mL), acidified with saturated citric acid solution and filtered. The solid was further washed with water and dried under vacuum to afford 250 mg (57%) of 4,6-dicyano-1H-indole-2-carboxylic acid (I-2b) as a light brown solid.

Provenance & Evidence