5,7-Difluoroindole

500139-00-4

301856-25-7

Example 4: Synthesis of the intermediate 5,7-difluoro-1H-indole To a solution of ethanol (35 mL) containing NaOEt (1.83 g, 26.9 mmol), a solution of ethyl (2,4-difluoro-6-trimethylsilylethynylphenyl)carbamate (2 g, 6.73 mmol) in ethanol (10 mL) was slowly added. The reaction mixture was stirred at room temperature for 1 h (monitored by TLC until the disappearance of the feedstock), followed by refluxing for 1 h. The reaction was completed by cooling to room temperature. After completion of the reaction, it was cooled to room temperature and the reaction mixture was concentrated under vacuum. The residue was dissolved in ether (50 mL) and washed sequentially with dilute hydrochloric acid (3 x 25 mL) and saturated saline (3 x 25 mL). The organic layer was dried with anhydrous Na2SO4, filtered and concentrated in vacuum. Purification by silica gel fast column chromatography (eluent ratio 1:4 ethyl acetate:hexane) gave 770 mg of the title compound in 75% yield.