Ethyl-2,4-dioxohexanoate → Ethyl 1,5-diethylpyrazole-3-carboxylate

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Reaction Steps

Ethyl 2,4-dioxohexanoate (21.5 g) in glacial acetic acid (125 ml) was cooled in an ice-bath and treated with N-ethylhydrazine oxalate (18.75 g) over 15 minutes. After addition was complete the mixture was stirred for 3 hours at room temperature. The acetic acid was then removed by evaporation in vacuo. The orange oily residue was dissolved in EtOAc and the solution washed repeatedly with saturated aqueous NaHCO3 and once with brine. Following drying over MgSO4 the solvent was evaporated in vacuo to give ethyl 1,5-diethylpyrazole-3-carboxylate as an oil (20.7 g); δ(CDCl3) 1.25-1.45 (9H, 3×3H,t, J 7 Hz), 2.62 (2H, q, J 7 Hz), 4.17 (2H, q, J 7 Hz), 4.38 (2H, q, J 7 Hz), 6.57 (1H, s) ppm.

Provenance & Evidence