1256359-15-5

70951-85-8

61676-62-8

1256359-15-5

4-Bromo-1-tert-butyl-1H-pyrazole (1.15 kg, 5.66 mol) and THF (9.2 L) were added to a 20 L four-necked flask and the mixture was cooled to -78°C to -85°C. At this temperature, n-butyllithium (nBuLi, 6.23 mol) was added dropwise. After addition, the reaction solution was continued to be stirred at the same temperature for 1 h. Subsequently, isopropyl pinacol borate (1.47 kg, 7.92 mol) was added dropwise. The reaction solution was stirred for about 3 hours until the reaction was complete (<1.0% feedstock residue by GC). The reaction was quenched by the addition of water (2.3 L) and the pH was subsequently adjusted to 8-9 with 1 M HCl (3.45 kg).The aqueous phase was extracted with tert-butyl methyl ether (TBME, 3.45 L x 2) and the combined organic phases were washed sequentially with 5% NaCl aqueous solution (3.45 L x 2) and water (3.45 L). The organic phase was evaporated to give the crude product. The crude product was purified by recrystallization from heptane to give a pure product in the form of a white solid (99.7% GC purity) with a total yield of 63.5%. Note: Two identical reactions on a 20 L scale were carried out, combined and recrystallized in heptane.