Triisopropyl borate → 3,5-Dimethylphenylboronic acid

To a solution of 5-bromo-m-xylene (1.5 g in 15 mL of dry tetrahydrofuran) at -78° C. was added 6.4 mL of a 1.4M solution of butyllithium in hexane and the mixture stirred for 20 minutes. At this time triisopropyl borate (2.8 mL) was added and the mixture allowed to warm to room temperature. After 1.5 hours the reaction was concentrated in vacuo to 1/3 volume then cooled to 0° C. and treated with 2N hydrochloric acid (9 mL) followed by warming to room temperature. After 4 hours the mixture was made basic by the addition of 2.5M sodium hydroxide and partitioned between ethyl ether (75 mL) and 1.25M sodium hydroxide. The organic layer was extracted with 1.25M sodium hydroxide (2×) and the aqueous portion then cooled to 0° C. and acidified to pH 3 by the dropwise addition of conc. hydrochloric acid. The white slurry was dissolved in methylene chloride, the organic portion dried over magnesium sulfate and concentrated in vacuo to provide the title compound (960 mg).

1. concentrationAfter 1.5 hours the reaction was concentrated in vacuo to 1/3 volume
2. temperaturethen cooled to 0° C.
3. additiontreated with 2N hydrochloric acid (9 mL)
4. temperatureby warming to room temperature
5. additionAfter 4 hours the mixture was made basic by the addition of 2.5M sodium hydroxide
6. custompartitioned between ethyl ether (75 mL) and 1.25M sodium hydroxide
7. extractionThe organic layer was extracted with 1.25M sodium hydroxide (2×)
8. temperaturethe aqueous portion then cooled to 0° C.
9. additionacidified to pH 3 by the dropwise addition of conc. hydrochloric acid
10. dissolutionThe white slurry was dissolved in methylene chloride
11. dry with materialthe organic portion dried over magnesium sulfate
12. concentrationconcentrated in vacuo

ORD record

ord-e2a927753a414f6d952bcf053c438427

Source dataset

uspto-grants-1998_05

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05756507