Sodium Hydroxide → (2-(1-methyl-1H-pyrazol-5-yl)-4-(trifluoromethyl)phenyl)boronic acid

Participants

Reaction Conditions

Reaction Steps

An 250-mL round-bottom flask was charged with 5-(2-bromo-5-(trifluoromethyl)phenyl)-1-methyl-1H-pyrazole (2.956 g, 9.69 mmol), diethyl ether (74.5 ml), and triisopropyl borate (2.70 ml, 11.63 mmol). The flask was cooled to −78° C. for 10 minutes, after which butyllithium (2.5M in hexanes) (4.65 ml, 11.63 mmol) was added dropwise. The mixture was stirred for 30 min, then warmed to room temperature. A 2N aq. NaOH solution (100 mL), and the resulting biphasic mixture was stirred vigorously for 1 h. The mixture was diluted with water, and the layers separated. The ethereal layer was extracted with water (2×) and the water layers were combined, and washed with diethyl ether. The ether layers were back-extracted once more, and all aqueous layers combined and acidified to about pH 2 with 6N aq HCl to give a clear solution. The aqueous layer was extracted with ethyl acetate (2×), and the combined organics were dried over sodium sulfate, filtered and concentrated. The residue was concentrated from DCM to give (2-(1-methyl-1H-pyrazol-5-yl)-4-(trifluoromethyl)phenyl)boronic acid (2.36 g, 8.74 mmol, 90% yield) as a yellow solid. m/z (ESI) 271.2 (M+H)+.

Provenance & Evidence