Hydrochloric Acid → 4,6-Dichloro-1H-indole-2-carboxylic acid

Participants

Reaction Steps

To a solution of ethyl 4,6-dichloro-1H-indole-2-carboxylate (I-1c: 50 g, 193.72 mmol) in a solvent mixture consisting of THF & water (1:1) (900 mL) was added LiOH.H2O (24.41 g, 581.7 mmol) and the reaction mixture stirred at room temperature for 18h. The solvent (THF) was distilled-off, the residue was diluted with water (400 mL) and acidified with 2N aqueous HCl to pH 6.0. The residue was extracted in to ethyl acetate (4×150 mL), combined organic layer washed with brine (350 ml), dried on anhydrous Na2SO4 and concentrated under reduced pressure to obtain 39 g (87.5%) of 4,6-dichloro-1H-indole-2-carboxylic acid (I-1d) as light brown solid.

Provenance & Evidence