100846-24-0

In 3-Naphthylindole construction by rhodium (II)-catalyzed regioselective direct arylation of indoles with 1-diazonaphthalen-2-(1H)-ones treatment of 5-(trifluoromethyl)indole(1k) or 6-(trifluoromethyl)indole (1l) with 2a afforded the desired products 3k (86%)and 3l (86%).

Step 5 Synthesis of 5-(trifluoromethyl)indole To a 250 mL three-necked round-bottomed flask was added N-[2-(3,3-dimethyl-3-silyl-1-ynyl)-4-(trifluoromethyl)phenyl]ethoxycarboxamide (31.5 g, 0.1 mol), EtONa (32.5 g, 0.48 mol) and anhydrous ethanol (200 mL). The reaction mixture was heated to reflux and kept for 2 hours. After completion of the reaction, the mixture was concentrated under reduced pressure. The residue was purified by fast column chromatography on silica gel, using a petroleum ether solution of 25% ethyl acetate as eluent to give 14 g (77% yield) of the target product 5-(trifluoromethyl)indole. 1H NMR (300 MHz, DMSO-d6) δ: 8.36 (s, 1H), 7.96-7.94 (m, 1H), 7.46-7.44 (m, 2H), 7.32-7.30 (m, 1H), 6.66-6.64 (m, 1H).

[1] Patent: US2010/120741, 2010, A1. Location in patent: Page/Page column 92
[2] Patent: WO2011/112731, 2011, A2. Location in patent: Page/Page column 197-198