Step 3: Ethyl 6-chloro-2,3,4,9-tetrahydro-1H-carbazole-1-carboxylate (1 g, 3.60 mmol, 1.00 eq.) was added to a 30 mL high-pressure reactor with a methanol solution of NH3 (7 M, 15 mL). The reactor was sealed and the reaction was stirred at 100 °C for 15 hours. Upon completion of the reaction, the reaction mixture was concentrated under reduced pressure to remove the solvent. The crude product was purified by preparative high performance liquid chromatography (HPLC) under the following conditions: the column was a Bridge Shield RP18 OBD column (5 μm, 19×150 mm); the mobile phases were water (containing 0.05% trifluoroacetic acid) and acetonitrile (acetonitrile ratio was increased from 31.0% to 42.0% in 10 min); the detection wavelength was UV 254/ 220 nm.The final product was 6-chloro-2,3,4,9-tetrahydro-1H-carbazole-1-carboxamide 400 mg (45% yield) as a white solid. The structure of the product was confirmed by NMR hydrogen spectroscopy (400 MHz, DMSO-d6): δ 10.81 (s, 1H), 7.44-7.36 (m, 2H), 7.29 (m, 1H), 7.10 (s, 1H), 7.00 (m, 1H), 3.66 (m, 1H), 2.64-2.56 (m, 2H), 2.11-1.89 (m , 3H), 1.70 (m, 1H). Liquid chromatography-mass spectrometry (LC-MS) analysis showed m/z = 249 [M + H]+.
