Lithium Hydroxide → 6-bromo-8-carbamoyl-9H-carbazole-2-carboxylic acid

Participants

Reaction Steps

A solution of ethyl 6-bromo-8-carbamoyl-9H-carbazole-2-carboxylate (4.7 g, 8.85 mmol) and lithium hydroxide (0.848 g, 35 4 mmol) in THF/EtOH/H2O (3/1/1) (70 mL) was heated at 75° C. overnight. The reaction was concentrated and the resulting yellow solid was suspended in water. To above suspension, was added 1M HCl/conc. HCl until pH=2-3. The light yellow solid was collected by filtration and air-dried to furnish 8.4 g of 6-bromo-8-carbamoyl-9H-carbazole-2-carboxylic acid with ˜80% purity. This material was carried forward to the next step. MS (ESI) m/z−=331/363 [M−H]−, 1 Br isotope pattern. HPLC retention time 9.79 min. (Sunfire C18 3.5 μm, 4.6×150 mm column, 15 min gradient, 10-100% B, 1 mL/min. Solvent A: 5% CH3CN-95% H2O-0.1% TFA; Solvent B: 95% CH3CN-5% H2O-0.1% TFA). 1H NMR (DMSO-d6) δ ppm 13.0-12.65 (b, 1H), 11.80 (s, 1H), 8.65 (d, 1H, J=1.8), 8.39 (d, 1H, J=0.6), 8.30 (s, 1H), 8.29 (d, 1H, J=8.2), 8.20 (d, 1H, J=1.8), 7.79 (dd, 1H, J=1.5, 8.3), 7.66 (br. s., 1H).

Provenance & Evidence