3,4-Dichlorophenol → beta-Carbolin-3-carboxylic acid 3,4-dichlorophenyl ester

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Reaction Steps

A suspension of 2.5 g of β-carbolin-3-carboxylic acid in a mixture of 450 ml of dry tetrahydrofuran and 1.8 ml of triethylamine is boiled under reflux for 15 minutes and cooled to room temperature. Freshly distilled ethyl chloroformate (1.25 ml) dissolved in 50 ml of dry tetrahydrofuran is added dropwise with stirring over a period of 1 hour. The reaction mixture (1) is stirred for additionally 30 minutes. A solution of 1.9 g of 3,4-dichlorophenol in 25 ml of dry tetrahydrofuran is added to 0.5 g of a 55% sodium hydride dispersion in oil suspended in 75 ml of dry tetrahydrofuran. The solution of the phenolate is added to mixture (1). Stirring is continued for one hour, whereafter the reaction mixture is filtered and concentrated to approximately 50 ml in vacuo. Addition of water (250 ml) causes the ester to precipitate. The mixture is left at 5° C. overnight and filtered. The dry product (3.0 g; 71%) is recrystallized from xylene to give pure β-carbolin-3-carboxylic acid 3,4-dichlorophenyl ester which melts at 260°-261° C.

Provenance & Evidence