Regioselective Synthesis of 5-Trifluoromethyl Pyrazoles by the [1+4] Cyclization of Phenylhydrazones with N-Aryl Trifluoroacetimidoyl Iodides

Article abstract of DOI:10.1055/s-1997-3274

Treatment of the phenylhydrazone of a methyl ketone (2) or cyclohexanone (3) with N-aryl trifluoroacetimidoyl iodide (1) in the presence of excess sodium hydride resulted in a [1+4] cyclization to give 5-trifluoromethyl pyrazoles (4, 5) regioselectively. The structure of products 4 or 5 was confirmed by the ¹³C NMR spectra.