Triisopropyl borate → (2-(Pyridin-4-yl)-4-(trifluoromethyl)phenyl)boronic acid

Participants

Reaction Steps

A round bottom flask was charged with 4-(2-bromo-5-(trifluoromethyl)phenyl)pyridine (2.0 g, 6.62 mmol), diethyl ether (50.9 ml), and triisopropyl borate (1.845 ml, 7.94 mmol). The flask was cooled to −78° C. for 10 minutes after which butyllithium (1.7 M in hexanes) (4.67 ml, 7.94 mmol) was added dropwise. The reaction was stirred for 30 minutes. The dry-ice bath was removed and 2N aqueous NaOH solution (50 mL) was added. The resulting biphasic mixture was stirred vigorously for one hour. The mixture was diluted with water, and the layers were separated. The diethyl ether was then extracted with water (×2) and the water layers were combined and washed twice with diethyl ether. The aqueous layer was neutralized to about pH 7 with 1N aqueous HCl solution and extracted with ethyl acetate (three times). The combined organic layers were dried over sodium sulfate, filtered and concentrated to afford (2-(pyridin-4-yl)-4-(trifluoromethyl)phenyl)boronic acid as an off-white solid. m/z (ESI) 268.1 (M+H)+.

Provenance & Evidence