Selectfluor → 5-tert-Butyl-4-fluoro-2-methyl-2H-pyrazole-3-carboxylic acid ethyl ester

Participants

Reaction Conditions

Reaction Steps

5-tert-Butyl-2-methyl-2H-pyrazole-3-carboxylic acid ethyl ester (210 mg, 1.00 mmol) was added dropwise to a stirred solution of SELECTFLUOR® (531 mg, 1.50 mmol) in anhydrous acetonitrile (4 mL) under an Ar atmosphere. The resulting mixture was then stirred at 80° C. for 12 h, then cooled to room temperature, diluted with EtOAc (2 mL), and filtered. The solvent was removed under reduced pressure and the resulting residue was chromatographed on a 24-g SiO2 pre-packed column eluting with 0:1-1:4 EtOAc/hexanes to yield 5-tert-Butyl-4-fluoro-2-methyl-2H-pyrazole-3-carboxylic acid ethyl ester. 1H-NMRH-NMR (400 MHz, CDCl3) δ: 4.37 (q, J=7.2 Hz, 2H), 4.03 (d, J=1.0 Hz, 3H), 1.39 (t, J=7.1 Hz, 3H), 1.34 (s, 9H).

Provenance & Evidence