Boron tribromide → 4-bromo-1H-Indol-5-ol

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Reaction Steps

A solution of 4-bromo-5-methoxyindole (540 mg, 2.4 mmol) in dichloromethane (12 ml) was cooled to −40° C. under an atmosphere of nitrogen. Boron tribromide (4.8 ml of a 1M solution in dichloromethane, 4.8 mmol) was added dropwise then the mixture warmed to ambient temperature and stirred for 1 hour. The mixture was diluted with dichloromethane (5 ml) and washed with 2M aqueous hydrochloric acid (3 ml). The organic layer was separated, dried (MgSO4) and evaporated to give a dark oil. This was purified by silica column chromatography eluting with dichloromethane/ethyl acetate (8/2) to give 4-bromo-5-hydroxyindole (295 mg, 55%).

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