Hydrochloric Acid → B-(4′-Ethoxy-2′,3′-difluoro[1,1′-biphenyl]-4-yl)boronic acid

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Reaction Steps

The compound (3) (10.0 g) and THF (100 ml) were put in a reaction vessel under a nitrogen atmosphere, and cooled to −74° C. n-Butyllithium (1.57 M in a n-hexane solution; 22.4 ml) was added dropwise thereto in the temperature range of −74° C. to −70° C., and the mixture obtained was stirred for another 2 hours. Subsequently, trimethyl borate (4.0 g) in a THF (50 ml) solution was added dropwise thereto in the temperature range of −74° C. to −65° C., and the mixture was stirred for another 8 hours while allowing the temperature to come to 25° C. Then, the reaction mixture was poured into a vessel containing 1N-hydrochloric acid (100 ml) and ice-water (500 ml), and mixed. Ethyl acetate (300 ml) was added thereto and the mixture was allowed to be separated into organic and aqueous phases, and then an extractive operation was carried out. The organic phase obtained was fractionated, washed sequentially with a saturated aqueous solution of sodium hydrogencarbonate and brine, and then dried over anhydrous magnesium sulfate. The solvent was then distilled off under reduced pressure, giving 11.7 g of 4-ethoxy-2,3-difluoro-1,1′-biphenyl-4′-boronic acid (6). The yield based on the compound (3) was 81.1%.

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