Tributyl borate → (1-Isopropyl-1H-pyrazol-5-yl)boronic acid

Participants

Reaction Conditions

Reaction Steps

To a solution of isopropylpyrazole (5.0 g, 45.5 mmol) in THF (100 mL) was added n-butyl lithium (31 mL, 50 mmol, 1.6 M in hexane) at −78° C. The mixture was kept stirring at the same temperature for 30 min. and was allowed to warm to 0° C. and stirred for another 30 min. Before adding tri-n-butyl borate (12.6 g, 55 mmol) as one portion, the reaction mixture was cooled to −78° C. After addition, the mixture was stirred at −78° C. for 1 h. and was allowed to warm to r.t. slowly and stirred overnight. The reaction mixture was quenched by saturated ammonium chloride. The organic phase was separated and the aqueous phase was extracted with ethyl ether (50 mL×2). The combined organic phase was dried over anhydrous sodium sulfate. Solvent was removed to afford 1-isopropyl-1H-pyrazole-5-boronic acid as a viscous oil (5.7 g).

Provenance & Evidence