Water → 9-oxo-9H-pyrrolo[1,2-a]indole-5-carboxylic acid methyl ester

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Reaction Steps

In a 50 ml round-bottomed flask, 3 ml of a 1M solution of boron tribromide in dichloromethane are added, at ambient temperature, to a mixture of 260 mg of 2-pyrrol-1-ylisophthalic acid dimethyl ester (which can be prepared according to Helvetica Chim. Acta 1983, 66(7), 2135) dissolved in 4 ml of dichloromethane. The reaction medium is stirred at ambient temperature for 2 hours and then 5 ml of water are added. After separation by settling out, the aqueous phase is re-extracted with twice 15 ml of dichloromethane. The combined organic phases are washed with twice 20 ml of water, dried over magnesium sulphate, and evaporated to dryness under vacuum. The residue is chromatographed on silica gel (15-40 μm), elution being carried out with a mixture of dichloromethane and cyclohexane (50/50 v/v). 122 mg of 9-oxo-9H-pyrrolo[1,2-a]indole-5-carboxylic acid methyl ester are obtained in the form of a yellowish solid, the characteristics of which are identical to those of the product obtained by method 1.

Provenance & Evidence