The reaction of 1,1,1,5,5,5-hexafluoropentane-2,4-dione with hydrazines: a re-investigation

The reaction of 1,1,1,5,5,5-hexafluoropentane-2,4-dione with hydrazine (N2H4) in boiling ethanol gives 3,5- bis(trifluoromethyl)pyrazole but reaction with N-aryl or N-aroyl hydrazines gives the 1-aryl- or 1-aroyl-3,5- bis(trifluoromethyl)-4,5-dihydro-5-hydroxypyrazoles, as shown by NMR and mass spectra, in contrast to a previous report.