Triisopropyl borate → 3,5-Dimethylphenylboronic acid

Participants

Reaction Steps

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 ⅓ 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).

Provenance & Evidence