5-bromo-1H,2H,3H-pyrrolo(2,3-b)pyridin-2-one → 5-bromo-1H-pyrrolo[2,3-b]pyridine

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Reaction Steps

Under an argon atmosphere and in an anhydrous medium, 37.6 ml (37.6 mmol) of a 1M solution of borane-tetrahydrofuran complex in tetrahydrofuran are added at 0° C. and dropwise to a suspension of 2 g (9.4 mmol) of the compound obtained in Step B in 50 ml of anhydrous tetrahydrofuran. The reaction mixture is stirred for 35 minutes at room temperature and then evaporated to dryness. The residue is taken up in an aqueous 6M hydrochloric acid solution and heated until the solid has completely dissolved. After cooling, the solution is rendered alkaline with an aqueous 6M sodium hydroxide solution and extracted with ethyl acetate. After drying over magnesium sulphate and evaporation, an equimolar mixture of 5-bromo-7-azaindoline and 5-bromo-7-azaindole is obtained. The preceding residue, which is dissolved in 20 ml of acetic acid, is added at room temperature to a suspension of 4.10 g (15.3 mmol) manganese(III) acetate dihydrate in 20 ml of acetic acid. After 45 minutes' stirring at 75° C. the solution is evaporated to dryness and coevaporated with toluene. The residue, which is taken up in water, is rendered alkaline with an aqueous saturated sodium hydrogen carbonate solution. After extraction with ethyl acetate the organic phases are dried over magnesium sulphate and evaporated. The resulting residue is purified by flash chromatography over silica gel (eluant:petroleum ether/ethyl acetate) to yield the title compound in the form of a yellow solid.

Provenance & Evidence