Boron tribromide → 4-[4-(4-Ethyl-5-fluoro-2-hydroxyphenoxy)-3-fluorobenzoyl]piperazin-2-one

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Reaction Steps

To a solution of 4-[4-(4-ethyl-5-fluoro-2-methoxyphenoxy)-3-fluorobenzoyl]piperazin-2-one (38 mg, 0.10 mmol; which may be prepared as described in D3) in dichloromethane (300 μL) under Argon cooled at −30° C. was added dropwise boron tribromide (1M in dichloromethane, 273 μL, 0.27 mmol). The mixture was allowed to come to room temperature and after stirring 20 h, was diluted with dichloromethane. The mixture was quenched carefully at 0° C. with an aqueous saturated solution of ammonium chloride and then diluted with ethyl acetate. The aqueous layer was extracted twice with ethyl acetate and the combined organic phases were washed with brine, dried over sodium sulfate, filtrated and concentrated in vacuo. The residue was purified by preparative thin layer chromatography on silica gel, using dichloromethane/methanol (95:5) as eluent. The title product was obtained as a white solid (32 mg, 86%).

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