16A. Synthesis of 6-(trifluoromethyl)-2,3,4,4a,9,9a-hexahydro-1H-carbazole
To a solution of 4-(trifluoromethyl)phenylhydrazine (4.71 g, 26.74 mmol) in ethanol (20 mL) was added concentrated hydrochloric acid (10 drops) followed by a solution of cyclohexanone (2.62 g, 26.74 mmol) in ethanol (4 mL). The reaction mixture was stirred at room temperature for 45 minutes and subsequently concentrated under vacuum. The resulting solid was dissolved in a mixture of acetic acid (21 mL) and concentrated sulfuric acid (3.5 mL). The reaction mixture was heated at 85 °C for 30 min, cooled to room temperature and poured into ice water. The suspension formed was filtered and the solid was dried to give 6-(trifluoromethyl)-2,3,4,9-tetrahydro-1H-carbazole as a brown solid (6.01 g, 94% yield). Mass spectrum (electrospray positive ion mode) m/e 240 [M + H]+.
