4-Butoxy-2,3-difluorophenylboronic acid

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The compound (23) (40.0 g) and acetic acid (100 ml) were put in a reaction vessel under a nitrogen atmosphere, and hydrogen peroxide (31% aqueous solution; 40.4 ml) was added dropwise in the temperature range of 25° C. to 30° C., and the stirring was continued for another 2 hours. Then the reaction mixture was poured into a vessel containing sodium hydrogen sulfite solution (100 ml) and ethyl acetate (300 ml), and mixed. Then the mixture was allowed to separate into organic and aqueous phases, and the extraction was carried out. The organic phase obtained was washed sequentially with water and brine, and dried over anhydrous magnesium sulfate. Then the solvent was distilled off under reduced pressure, giving 31.7 g of 4-butoxy-2,3-difluorophenol (24). The yield based on the compound (23) was 90.2%. Then the reaction mixture was poured into a vessel mixed to separate into organic and aqueous phases the extraction The organic phase obtained was washed sequentially with water and brine dried over anhydrous magnesium sulfate Then the solvent was distilled off under reduced pressure

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The compound (22) (84.6 g) and THF (500 ml) were put in a reaction vessel under a nitrogen atmosphere, and cooled to −74° C. n-Butyllithium (1.65 M in a n-hexane solution; 303.0 ml) was added dropwise in the temperature range of −74° C. to −70° C., and the stirring was continued for another 2 hours. Then, the mixture was added dropwise to a THF (200 ml) solution of trimethyl borate (56.7 g) in the temperature range of −74° C. to −65° C., and the stirring was continued for another 8 hours while the mixture was allowed to return to 25° C. Subsequently, the reaction mixture was poured into a vessel containing 1N—HCl (100 ml) and ice-water (500 ml), and mixed. Ethyl acetate (300 ml) was added thereto and the mixture was allowed to separate into organic and aqueous phases, and the extraction was carried out. The organic phase obtained was washed sequentially with water, a saturated aqueous solution of sodium hydrogencarbonate and brine, and dried over anhydrous magnesium sulfate. Then the solvent was distilled off under reduced pressure, giving 4-butoxy-2,3-difluorophenylboronic acid (23) (6.4 g). The yield based on the compound (22) was 69.2%. 303.0 ml) was added dropwise in the temperature range of −74° C. to −70° C. the stirring was continued for another 8 hours while the mixture to return to 25° C Subsequently, the reaction mixture was poured into a vessel mixed to separate into organic and aqueous phases the extraction The organic phase obtained was washed sequentially with water a saturated aqueous solution of sodium hydrogencarbonate and brine, and dried over anhydrous magnesium sulfate Then the solvent was distilled off under reduced pressure