327-21-9

2261-08-7

327-21-9

To a 1000 mL three-necked flask was added (E)-ethyl-2-(2-(3-(trifluoromethyl)phenyl)hydrazinyl)propionate (26 g, 94.8 mmol) synthesized in Step 1 and toluene. Subsequently, polyphosphoric acid (150 g) was slowly added to the reaction system, heated to reflux and maintained for 6 hours. After completion of the reaction, the reaction mixture was cooled to 50°C and the toluene layer was separated. The toluene layer was concentrated to dryness under reduced pressure. Toluene (50 mL) was added to the resulting solid, refluxed for 1 hour and cooled to room temperature. The recrystallized product was collected by filtration to afford ethyl 6-(trifluoromethyl)-1H-indole-2-carboxylate (1.25 g, 4.86 mmol, 5% yield).