Methyl acetoacetate → 1-(4-fluorophenyl)-3-methyl-4,5-dihydro-1H-pyrazol-5-one

Participants

Reaction Conditions

Reaction Steps

To a solution of 3-oxo-butyric acid methyl ester (2.8 g) in acetic acid (6.5 mL) in a round bottom flask under argon was added 4-fluorophenylhydrazine (3.05 g). The mixture was immersed into an oil bath and heated to 120° C. overnight. The reaction vessel was then cooled and the acetic acid was evaporated in vacuo and the remaining solid was dissolved in EtOAc and water. The phases were separated and the aqueous phase was extracted with further EtOAc. The combined organic phases were washed with brine, dried over sodium sulfate, filtered and evaporated in vacuo and azeotroped with toluene (2×). The crude residue was then purified via ISCO Combiflash chromatography using EtOAc/heptane as eluent to afford the desired 2-(4-fluoro-phenyl)-5-methyl-2,4-dihydro-pyrazol-3-one (3.2 g) as a beige solid. MS (ESI+): 193.3 ([M+H]+).

Provenance & Evidence