Triisopropyl borate → (2,3-Dimethylpyridin-4-YL)boronic acid

Temperature

-20 °C

A solution of 4-bromo-2,3-dimethyl-pyridine (1.38 g) and triisopropyl borate (2.05 mL) in 4 mL dry THF and 14 mL dry toluene was stirred on a dry ice-aceton bath to an internal temperature of −65° C. and 3.56 mL n-BuLi in hexanes was added dropwise over 0.5 h. Stirring continued at −65° C. for additional 2 h, then the bath was removed the mixture allowed to warm to −20° C. Reaction was quenched by addition of 10 mL 2M HCl, then allowed to warm to rt and diluted with more THF. 5M NaOH was added until the mixture reached pH 7, layers formed and the organic layer was collected. Several more extractions with THF were done and the combined organic extracts were dried with brine and Na2SO4 and concentrated under reduced pressure. The product crystallized and two crops were collected, for a total of 304 mg of 2,3-dimethylpyridine-4-boronic acid. LCMS (m/z) 153.

1. additionwas added dropwise over 0.5 h
2. customthe bath was removed the mixture
3. customReaction
4. customwas quenched by addition of 10 mL 2M HCl
5. temperatureto warm to rt
6. additiondiluted with more THF
7. addition5M NaOH was added until the mixture
8. customformed
9. customthe organic layer was collected
10. extractionSeveral more extractions with THF
11. dry with materialthe combined organic extracts were dried with brine and Na2SO4
12. concentrationconcentrated under reduced pressure
13. customThe product crystallized
14. customtwo crops were collected, for a total of 304 mg of 2,3-dimethylpyridine-4-boronic acid

ORD record

ord-d0411694b7d8434589e28eb36e26f2d1

Source dataset

uspto-grants-2013_02

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08383644B2