Boron tribromide → 5-Bromo-4'-fluoro[1,1'-biphenyl]-2-ol

Participants

Reaction Steps

A mixture of 4′-fluoro[1,1′-biphenyl]-2-yl methyl ether (107 g), pyridinium hydrobromide perbromide (34.0 g) and water-acetic acid-diethyl ether mixed solution (1:4:5, 500 ml) was stirred for 18 h at room temperature. Hypowater was added to the reaction mixture and the mixture was concentrated. The resulting crystals were collected by filtration to give a crude product (15.2 g) of 5-bromo-4′-fluoro[1,1′-biphenyl]-2-yl methyl ether as a yellow solid. To a solution of this product (14.1 g) in dichloromethane (150 ml) was added dropwise a solution of boron tribromide (5.69 ml) in dichloromethane (40 ml) at −78° C., and the mixture was stirred at room temperature ifor 18 h. The reaction mixture was poured into ice and the organic layer was separated, neutralized with aqueous sodium hydrogen carbonate, washed with brine and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure and the residue was purified by silica gel chomatography (eluent;hexane→hexane:ethyl acetate=5:1) to give the title compound (13.2 g) as a colorless oil.

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