4-Bromophenylhydrazine hydrochloride → HCID 57437901, compound

Participants

Reaction Steps

Ethyl-2-(cyclopropanecarbonyl)-3-dimethylamino-prop-2-enoate (Intermediate #32) (316 mg, 1.5 mmol) was dissolved in ethanol (5 mL). 4-bromophenylhydrazine hydrochloride (335 mg, 1.5 mmol) and DIPEA (264 μL, 1.5 mmol) were added and the mixture was heated to reflux for 2 h. The reaction mixture was cooled to ambient and evaporated under reduced pressure. The residue was dissolved in DCM (10 mL) washed with water and poured through a phase separating tube. The product was recovered from the filtrate by flash column chromatography (SiO2, elution gradient 0-25% EtOAc in isohexane). Pure fractions were combined and evaporated to give ethyl 1-(4-bromophenyl)-5-cyclopropyl-pyrazole-4-carboxylate as an oil that crystallised on standing. (343 mg, 87%)

Provenance & Evidence