Hydrochloric Acid → 4-(Trifluoromethyl)phenylboronic acid

Participants

Reaction Steps

An oven dried Schlenk tube was charged with magnesium turnings (766 mg, 31.5 mmol), evacuated, and backfilled with argon. To the reaction vessel was added 10 mL of ether followed by 4-(trifluoromethyl)phenyl bromide (4.20 mL, 30.0 mmol). The reaction mixture was stirred without external heating for 1 hour, during which time an exotherm occurred and then subsided. The solution was diluted with ether (10 mL) and transferred via cannula to a flask containing triisopropylborate (13.8 mL, 60.0 mmol) in 1:1 THF/ether (20 mL) at −78° C. The resulting reaction mixture was kept at −78° C. for 15 minutes and then was allowed to warm to room temperature. After stirring at room temperature for 15 minutes, the reaction mixture was poured onto 2.0 M HCl (60 mL). The mixture was transferred to a separatory funnel, extracted with ethyl acetate (60 mL), washed with water (60 mL), and brine (60 mL). The organic solution was dried over anhydrous sodium sulfate and concentrated in vacuo. The crude material was dissolved in 2:1 hexane/ethyl acetate (90 mL) and activated charcoal was added. The mixture was filtered and the product crystallized upon cooling. The crystals were collected by filtration to afford 1.98 g (35%) of pale yellow needles.

Provenance & Evidence