Water → Ethyl 1-ethyl-5-methyl-1H-pyrazole-3-carboxylate

Participants

Reaction Steps

N-Ethylhydrazine oxalate (12 g) in glacial acetic acid (100 ml) was cooled in an ice-bath and treated with ethyl 2,4-dioxovalerate (11.24 ml). After addition was complete the mixture was stirred at room temperature; after ca. 45 min the mixture was warmed to dissolve insoluble ethylhydrazine oxalate. The mixture was stirred for a further 2 h and then poured into water(ca. 300 ml)/ethyl acetate (ca. 700 ml) and solid K2CO3 was carefully added, with stirring, until the pH was neutral. After separation the aqueous layer was re-extracted with ethyl acetate. The combined ethyl acetate extracts were dried (MgSO4), and the solvents removed to leave an oil. Chromatography on silica gel, loading in CH2Cl2 /hexane and eluting with a gradient elution of ethyl acetate/hexane mixtures (from 2:8 to 1:1) gave ethyl 1-ethyl-5-methylpyrazole-3-carboxylate as an oil (13.2 g); νmax (CH2Cl2) 1717, 1446, 1389, and 1219 cm-1 ; δ(CDCl3) 1.38 (3H, t, J 7.2 Hz), 1.42 (3H, t, J 7.3 Hz), 2.30 (3H, s), 4.17 (2H, q, J 7.3 Hz), 4.38 (2H, q, J 7.1 Hz), 6.55 (1H, s); (Found m/z 182.1055. C9H14N2O2 requires m/z 182.1055).

Provenance & Evidence