Ethyl 4-oxocyclohexanecarboxylate → 6-bromo-3-(ethoxycarbonyl)-2,3,4,9-tetrahydro-1H-carbazole-8-carboxylic acid

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Reaction Steps

To a stirred suspension of 5-bromo-2-hydrazinylbenzoic acid dihydrochloride (3.08 g, 10.13 mmol) in AcOH, (˜0.5M) (20 mL) was added ethyl 4-oxocyclohexanecarboxylate (1.759 g, 10.34 mmol) at room temperature. The cream-colored reaction mixture was then stirred under reflux for 4 h. The reaction mixture was cooled to room temperature and concentrated in vacuo to afford a yellow solid. The solid was then dissolved in ethyl acetate, washed with 1N aqueous HCl and brine solution. The organic phase was dried over Na2SO4 and concentrated to give the crude product, which was then suspended in ether and the yellow solid was collected by filtration, air-dried. Additional quantity was obtained by combining the filtrate followed by silica gel column chromatography (hexane/ethyl acetate=50/50-0/100) to give 2.1 g of 6-bromo-3-(ethoxycarbonyl)-2,3,4,9-tetrahydro-1H-carbazole-8-carboxylic acid. MS (ESI) m/z 367.2 (M+H). 1H NMR (DMSO-d6) δ ppm 13.2 (br s, 1H), 10.8 (s, 1H), 7.8 (s, 1H), 7.6 (s, 1H), 3.92 (m, 4H), 3.77 (q, 2H, J=7.8 Hz), 2.52-2.81 (m, 7H), 1.3 (t, 3H).

Provenance & Evidence