Lithium hydroxide, monohydrate → 9-oxo-9H-pyrrolo[1,2-a]indole-5-carboxylic acid

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Reaction Steps

In a 250 ml round-bottomed flask, a mixture of 800 mg of 9-oxo-9H-pyrrolo[1,2-a]indole-5-carboxylic acid methyl ester obtained according to the preceding stage and of 740 mg of lithium hydroxide monohydrate in 25 ml of water and 100 ml of methanol is refluxed for 3 hours. The reaction medium is evaporated to dryness under vacuum, and the solid is taken up in 35 ml of water and brought to pH 3 with 5M hydrochloric acid. A precipitate appears and the medium is extracted with 3 times 35 ml of a mixture of dichloromethane and methanol (95/5 v/v). The combined organic extracts are washed with 3 times 15 ml of water, dried over magnesium sulphate, and evaporated to dryness under vacuum. 630 mg of 9-oxo-9H-pyrrolo[1,2-a]indole-5-carboxylic acid are obtained in the form of a beige solid, the characteristics of which are the following:

Provenance & Evidence