Hydrochloric Acid → (3,5-Difluorophenyl)boronic acid

Temperature

-78 °C

In a separate reaction vessel, 40 mL of tetrahydrofuran was cooled to -78 ° C., and the Grignard reagent of 3,5-difluorophenyl bromide and a solution of 11.3 grams (0.109 mole) of trimethyl borate in 15 mL of tetrahydrofuran were added simultaneously dropwise in an effort to provide an equimolar addition of each. An additional 115 mL of tetrahydrofuran was added during the additions to dilute the thickening reaction mixture. The completion of additions required about 15 minutes. After this time the reaction mixture was allowed to warm to ambient temperature as it stirred for about 18 hours. The reaction mixture was then poured into 300 mL of an aqueous dilute solution of hydrochloric acid. The resultant mixture was extracted with two 150 mL portions of ethyl acetate. The combined extracts were dried with magnesium sulfate and filtered. The filtrate was concentrated under reduced pressure, yielding 13.6 grams of 3,5-difluoro-phenylboronic acid. The NMR spectrum was consistent with the proposed structure.

1. customto provide
2. additionan equimolar addition of each
3. additionto dilute
4. customthe thickening reaction mixture
5. customabout 15 minutes
6. temperatureto warm to ambient temperature as it
7. extractionThe resultant mixture was extracted with two 150 mL portions of ethyl acetate
8. dry with materialThe combined extracts were dried with magnesium sulfate
9. filtrationfiltered
10. concentrationThe filtrate was concentrated under reduced pressure

ORD record

ord-4cdb059ff8cc42ae854dcec042724c9f

Source dataset

uspto-grants-1997_05

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05627189