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

HRID 1898546Notes

Reaction equation

[CH:1]1([N:4]2[CH:8]=[C:7](I)[CH:6]=[N:5]2)[CH2:3][CH2:2]1.C([Mg]Cl)(C)C.C(O[B:19]1[O:23][C:22]([CH3:25])([CH3:24])[C:21]([CH3:27])([CH3:26])[O:20]1)(C)C>C1COCC1>[CH:1]1([N:4]2[CH:8]=[C:7]([B:19]3[O:23][C:22]([CH3:25])([CH3:24])[C:21]([CH3:27])([CH3:26])[O:20]3)[CH:6]=[N:5]2)[CH2:3][CH2:2]1

Participants

Conditions

Temperature: 0 °C

Procedure

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.

Workup

temperatureto warm to room temperature over 1 h
customThe mixture was quenched with 50%
extractionextracted with EtOAc
extractionThe organic extract
washwas washed with sat. NaCl
dry with materialdried over MgSO4
concentrationthe solution was concentrated
customThe residue was purified by SiO2 chromatography (20-50% EtOAc/heptane)

Sources & evidence

ORD record: ord-fe4d3f6b15f54933bbf70dadad884795
Source dataset: uspto-grants-2013_08
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US08518945B2

Reaction notes

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