2,3-Dichloro-5,6-dicyano-1,4-benzoquinone → 4-bromo-7-(ethoxycarbonyl)-3-fluoro-9H-carbazole-1-carboxylic acid

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Reaction Steps

A solution of 5-bromo-2-(ethoxycarbonyl)-6-fluoro-2,3,4,9-tetrahydro-1H-carbazole-8-carboxylic acid (2.87 g, 7.47 mmol) and 2,3-dichloro-5,6-dicyanobenzoquinone (3.73 g, 16.4 mmol) in THF (45 mL) was heated at 60° C. for 90 min. The cooled mixture was diluted with EtOAc (about 50 mL) and stirred for 60 min. The resulting precipitate was collected by filtration, washed with EtOAc and dried. The filtrate was concentrated, and the residue was triturated with MeOH with sonication, filtered, and the precipitate was washed with MeOH and dried. The two precipitates were combined to give 4-bromo-7-ethoxycarbonyl-3-fluoro-9H-carbazole-1-carboxylic acid as a pale yellow solid (2.39 g, 84% yield). Mass spectrum m/z 380, 382 (M+H)+.

Provenance & Evidence