Acetic Acid → 5-bromo-6-chloro-2-(ethoxycarbonyl)-2,3,4,9-tetrahydro-1H-carbazole-8-carboxylic acid

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

A suspension of 4-bromo-5-chloro-2-hydrazinylbenzoic acid hydrochloride (12.89 g, 37.6 mmol), ethyl 3-oxocyclohexanecarboxylate (7.03 g, 41.3 mmol), and acetic acid (6.45 mL, 113 mmol) in toluene (188 mL) was heated at 105° C. overnight. After 16 h, more acetic acid (6 mL) and ethyl 3-oxocyclohexanecarboxylate (2.00 g) were added and the mixture was heated at 110° C. for 4.5 h. The mixture was concentrated, and the residue was combined with toluene (100 mL) and TFA (20 mL). The suspension was heated at 90° C. overnight. The cooled mixture was concentrated and the residue was suspended in EtOAc. The resulting solid was collected by filtration, washed with EtOAc and air-dried to give 5-bromo-6-chloro-2-(ethoxycarbonyl)-2,3,4,9-tetrahydro-1H-carbazole-8-carboxylic acid as a yellow solid (11.0 g, 73% yield). Mass spectrum m/z 400, 402 (M+H)+. 1H NMR (400 MHz, DMSO-d6) δ 13.44 (br. s., 1H), 11.24 (s, 1H), 7.69 (s, 1H), 4.12 (qd, J=7.1, 2.3 Hz, 2H), 3.23-2.81 (m, 5H), 2.23-2.09 (m, 1H), 1.91-1.75 (m, 1H), 1.22 (t, J=7.0 Hz, 3H).

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