116650-34-1

97096-16-7

100-63-0

61894-99-3

General procedure for the synthesis of (S)-2,3,4,9-tetrahydro-1H-carbazol-3-amine from 8-amino-1,4-dioxaspiro[4,5]decane and phenylhydrazine: aqueous sulfuric acid (10% w/v, 30 mL) was added to a round-bottomed flask, followed by the addition of (1,4-dioxaspiro[4.5]dec-8-yl)dimethylamine (12a, 1.5 g, 8.1 mmol ). Phenylhydrazine (1.52 g, 14.08 mmol) was slowly added to the reaction mixture at room temperature. The reaction system was heated to reflux temperature (95-100°C) and maintained at reflux for 2-3 hours. The reaction process was monitored by thin layer chromatography (TLC). Upon completion of the reaction, the reaction mixture was cooled to 10-15°C. Subsequently, the pH was adjusted to alkaline with aqueous sodium hydroxide (20% w/v) and the aqueous phase was extracted with ethyl acetate. The organic layer was washed with saturated brine and dried with anhydrous sodium sulfate. The organic solvent was removed by distillation under reduced pressure to give the crude product. The crude product was purified by fast column chromatography (eluent: ethyl acetate/triethylamine = 9:0.2) to give (S)-2,3,4,9-tetrahydro-1H-carbazol-3-amine (13a, 0.8 g) in 50% yield.