反应详情

A suspension of ethyl 5-bromo-8-carbamoyl-9H-carbazole-2-carboxylate (Intermediate 48-1, 1.81 g, 5.01 mmol) and lithium hydroxide monohydrate (0.601 g, 15.03 mmol) in THF-ethanol-water (3:1:1, 50 mL) was heated at reflux for 2 h. The mixture was cooled to rt and concentrated. The residue was stirred in water and treated with 1 M hydrochloric acid to pH 1-2. The precipitate was collected by filtration, washed with water, and dried to afford 5-bromo-8-carbamoyl-9H-carbazole-2-carboxylic acid as a light brown solid (1.84 g, ca. 90% purity, 99%). 1H NMR (400 MHz, DMSO-d6) δ 12.95 (br. s., 1H) 12.02 (s, 1H) 8.69 (d, J=8.53 Hz, 1H) 8.47 (s, 1H) 8.28 (br. s., 1H) 7.94 (d, J=8.28 Hz, 2H) 7.87 (d, J=8.28 Hz, 1H) 7.65 (br. s., 1H) 7.51 (d, J=8.03 Hz, 1H). Mass spectrum m/z 331, 333 (M−H)−.

1. temperaturewas heated
2. temperatureat reflux for 2 h
3. concentrationconcentrated
4. additiontreated with 1 M hydrochloric acid to pH 1-2
5. filtrationThe precipitate was collected by filtration
6. washwashed with water
7. customdried