[H-].[Na+:2].C[Si](C#[C:8][C:9]1[CH:20]=[C:19]([F:21])[CH:18]=[C:17]([F:22])[C:10]=1[NH:11][C:12]([O:14][CH2:15][CH3:16])=O)(C)C.C(OCC)(=O)C.CCCCCC>C(O)C>[O-:14][CH2:15][CH3:16].[Na+:2].[F:21][C:19]1[CH:20]=[C:9]2[C:10](=[C:17]([F:22])[CH:18]=1)[NH:11][CH:12]=[CH:8]2Fresh sodium ethoxide is prepared by carefully adding NaH (16 g of 60% oil dispersion, 400 mmol) to 550 mL of ethanol under N2. 2-(Trimethylsilylethynyl)-4,6-difluoro-N-carbethoxyaniline (28 g, 100 mmol) in 150 mL of ethanol is added and reaction is stirred at room temperature approximately 45 minutes, while monitoring by TLC (20% ethyl acetate/hexane, UV) until all the starting material is consumed. The mixture is heated to reflux and monitored by TLC until the intermediate material is consumed (approx. 1 hour). Reaction is cooled to room temperature, concentrated, diethylether is added, washed with H2O, brine, dried (Na2SO4), filtered, concentrated, and is purified by flash chromatography (SiO2, ethyl acetate/hexane gradient) to yield 12 g of 5,7-difluoro-indole (78%).
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