Carbon Dioxide → 6-fluoro-1H-indole-7-carboxylic Acid

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

60 ml THF were cooled down to −60° C. under argon and 27 ml of a 1.6M n-BuLi solution (42.9 mmol) in hexane were added followed by 2.9 g of 6-fluoro-1H-indole (21 mmol) in 12 ml THF (addition over 25 min, temperature between −72 and −70° C.). After 5 min additional stirring at this temperature, a solution of 4.8 g of potassium tert-butylate (42.9 mmol) in 18 ml THF were added at the same temperature over 30 min. The reaction mixture was then stirred for 2 h at −72° C. and then treated with a large excess of solid CO2 over 1.5 h (temperature raised by 15° C.). To the brown/orange suspension, 40 ml of water were added, and after addition of diethylether the phases were separated, the aqueous phase extracted with 2× diethylether. Finally the aqueous phase was treated with conc HCl until pH 1 and extracted twice with diethylether. The combined organic phases were then washed with brine, dried over magnesium sulfate, filtered and concentrated in vacuo, and crystallized from diethylether/hexane, leading to 1.9 g 6-fluoro-1H-indole-7-carboxylic acid, as a light brown solid (51%). MS: 177.9 (M−H)−

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