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

To a stirred solution of 4-bromo-3-cyclopropyl-1-methyl-1H-pyrazole (500 mg, 2.5 mmol) in THF (10 mL) was added dropwise a 2.5 M solution of n-BuLi (1.4 mL, 3.5 mmol) at −78° C., and the resulting light yellow solution was stirred for 30 min. To the mixture was added a solution of 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (1.1 mL, 5.5 mmol) in THF (1 mL), and the mixture was warmed to room temperature over 30 min. The reaction was quenched with saturated aqueous NH4Cl solution. The mixture was extracted with EtOAc (50 mL), washed with brine, dried over MgSO4, filtered and concentrated under reduced pressure. The residue was purified by normal phase flash chromatography on silica gel (5% MeOH—CH2Cl2, Rf=0.35) to provide 3-cyclopropyl-1-methyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (294 mg, 48%) as a yellow oil.

1. customThe reaction was quenched with saturated aqueous NH4Cl solution
2. extractionThe mixture was extracted with EtOAc (50 mL)
3. washwashed with brine
4. dry with materialdried over MgSO4
5. filtrationfiltered
6. concentrationconcentrated under reduced pressure
7. customThe residue was purified by normal phase flash chromatography on silica gel (5% MeOH—CH2Cl2, Rf=0.35)

ORD record

ord-7f71f72d1a694998acb79f8d32570318

Source dataset

uspto-grants-2013_11

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08575360B2