2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane → 1-Cyclopropyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole

Participants

Reaction Conditions

Reaction Steps

In a flask 1-cyclopropyl-4-iodo-1H-pyrazole (405 mg, 1.73 mmol) was dissolved in THF (8.0 mL) and the solution cooled to 0° C. Isopropylmagnesium chloride (2.0 M in THF, 1.04 mL, 2.08 mmol) was added dropwise and the mixture stirred at 0° C. for 45 min, after which 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (0.53 mL, 2.60 mmol) was added and the mixture allowed to warm to room temperature over 1 h. The mixture was quenched with 50% sat aqueous NH4Cl and extracted with EtOAc. The organic extract was washed with sat. NaCl, dried over MgSO4 and the solution was concentrated. The residue was purified by SiO2 chromatography (20-50% EtOAc/heptane) to afford 405 mg (83%) of 1-cyclopropyl-1H-pyrazole-4-boronic acid pinacol ester as a colorless viscous oil.

Provenance & Evidence