Trimethyl borate → (4-Chloro-2-methoxyphenyl)boronic acid

Temperature

-78 °C

4-Chloro-2-methoxyphenylboronic acid ethylene glycol ester To a solution of 2-bromo-5-chloroanisole (4.43 g, 20 mmol) in dry THF (100 mL) at −78° C. was added dropwise t-BuLi (14.1 mL, 1.7 M, 23.97 mmol). The mixture was stirred for 10 min at −78° C. and trimethyl borate (2.23 mL, 20 mmol) was added. The cooling bath was removed and the mixture was stirred for 30 min from −78° C. to room temperature and then for 3 h with a water bath. Hydrochloric acid (6N, 8 mL) and brine were added. The mixture was extracted with ethyl acetate, dried and evaporated to give 4-chloro-2-methoxyphenylboronic acid as a brown solid (3.33 g, 17.88 mmol) in 89.4% yield. This boronic acid was mixed with ethylene glycol (1.1 g, 17.88 mmol) and toluene (150 mL). The mixture was refluxed for 2 h under N2 with the help of a Dean-Stark trap to remove water generated. After being cooled to room temperature, the solution was transferred to another dry flask and rotary evaporated to provide 4-Chloro-2-methoxyphenylboronic acid ethylene glycol ester as a brown liquid (3.6 g, 16.97 mmol) in 84.8% yield.

1. customThe cooling bath was removed
2. stirringthe mixture was stirred for 30 min from −78° C. to room temperature
3. waitfor 3 h with a water bath
4. additionHydrochloric acid (6N, 8 mL) and brine were added
5. extractionThe mixture was extracted with ethyl acetate
6. customdried
7. customevaporated

ORD record

ord-8e971f5f98e84c6c96b5255ae1df5d16

Source dataset

uspto-grants-2008_12

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07465836B2