Water → Ethyl 3-difluoromethyl-1-methyl-4-pyrazole carboxylate

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Reaction Steps

The aminal (1.00 g, 2.81 mmol) was dissolved in 7 mL of toluene. Then, ethyl α-ethoxymethylene-4,4-difluoro-3-oxobutyrate (1.25 g, 5.62 mmol) and p-TsOH (107 mg, 0.56 mmol) were added, followed by water (101 mg, 5.62 mg). The mixture was stirred at rt for 90 min, then GC control showed >97% conversion to the pyrazole. The reaction mixture was extracted with water (2×1 mL); then, the organic phase was concentrated under reduced pressure and the residue purified by column chromatography (SiO2, cyclohexane/EtOAc 100:0→70:30) to give the product (840 mg, 4.12 mmol, 73% yield) as a colorless solid.

Provenance & Evidence