3-Bromo-5-fluorobenzoic acid → (3-Bromo-5-fluorophenyl)methanol

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Reaction Steps

Sodium borohydride (1.68 g) was added to diethylene glycol dimethyl ether (40 ml). While the mixture was stirred at room temperature, 3-bromo-5-fluorobenzoic acid (9.72 g) was added portionwise (six portions). After the crystals were completely dissolved, trifluoroborane ether complex (8.40 g) in diethylene glycol dimethyl ether (10 ml) was added dropwise thereto. The mixture was stirred for 5 hours, and poured into ice/water. The mixture was extracted with ether (200 ml), and washed with water, followed by drying over magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography (n-hexane:ethyl acetate=10:1→5:1), to thereby yield a mixture of the target compound and diethylene glycol dimethyl ether. The thus-obtained mixture was analyzed by NMR to determine the content of diethylene glycol dimethyl ether. The content and the yield of the target compound as determined by NMR were 7.70 g and 84.6%, respectively.

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