Hydrochloric Acid → 4-Chloro-1H-pyrrolo[2,3-b]pyridine

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Reaction Conditions

Reaction Steps

750 mg (5.63 mmol) of 4-amino-1H-pyrrolo[2,3-b]pyridine (from example XVII) are dissolved in a mixture of 67.5 ml of glacial acetic acid and 0.67 ml of concentrated sulfuric acid. The mixture is cooled to 12° C. 3.67 ml (3.20 g, 117 mmol) of isopentyl nitrite are slowly added dropwise, and the mixture is stirred at 12° C. for 3 hours. This solution is then added to a suspension (temperature: 50° C.) of 6.07 g (61.4 mmol) of copper(I) chloride in 34 ml of concentrated hydrochloric acid, and the mixture is then heated at 80-90° C. for 30 min. The mixture is cooled to RT and stirred overnight. For work-up, the reaction solution is concentrated and made alkaline using 1N aqueous sodium hydroxide solution, the precipitated copper salts are filtered off with suction through kieselguhr and the mixture is extracted 3× with ethyl acetate. The organic phase is dried over magnesium sulfate and concentrated using a rotary evaporator.

Provenance & Evidence