1,3-Diethyl 2-(3-oxocyclohexyl)propanedioate → 5-bromo-2-(1,3-diethoxy-1,3-dioxopropan-2-yl)-6-fluoro-2,3,4,9-tetrahydro-1H-carbazole-8-carboxylic acid

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A solution of diethyl 2-(3-oxocyclohexyl)malonate (15.26 g, 59.5 mmol) and 4-bromo-5-fluoro-2-hydrazinylbenzoic acid hydrochloride [Intermediate 24B] (17.0 g, 59.5 mmol) in acetic acid (120 mL) was heated at reflux for 2 h, then was stirred overnight at room temperature. The precipitate which formed was collected by filtration to provide a white solid. The filtrate was concentrated and purified by column chromatography on silica gel (80 g), eluting with EtOAc-hexanes (gradient from 0-100%). The resulting oily product was crystallized from a mixture of EtOAc, ether and hexanes to provide additional solid, which was combined with the first solid to provide 5-bromo-2-(1,3-diethoxy-1,3-dioxopropan-2-yl)-6-fluoro-2,3,4,9-tetrahydro-1H-carbazole-8-carboxylic acid as a white solid (10.5 g, 49% yield). Mass spectrum m/z 470, 472 (M+H)+.

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