3-Cyano-4-fluorophenylhydrazine hydrochloride → tert-butyl 1-(3-cyano-4-fluorophenyl)-5-(2-furyl)-1H-pyrazole-3-carboxylate

Participants

Reaction Steps

Part A. To lithium 1-tert-butoxy-4-(2-furyl)-1,4-dioxo-2-buten-2-olate (13 g, 54 mmol; Example 74, Part A) was added 2-fluoro-5-hydrazinobenzonitrile hydrochloride (10 g, 54 mmol) and 250 mL of glacial acetic acid. The resulting orange mixture was maintained at rt for 20 h and then concentrated to dryness. The resulting residue was taken up in 30% chloroform in hexanes and filtered to afford tert-butyl 1-(3-cyano-4-fluorophenyl)-5-(2-furyl)-1H-pyrazole-3-carboxylate (18 g, 95%) as a light brown solid. LC/MS (ESI+): 354.2 (M+H)+. 1H NMR (CDCl3) δ 7.64–7.78(m, 3H), 7.42 (s, 1H), 7.05 (s, 1H), 6.45 (s, 1H), 6.30 (s, 1H), 1.61 (s, 9H).

Provenance & Evidence