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Synlett 1997; 1997(6): 679-680
DOI: 10.1055/s-1997-3274
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Regioselective Synthesis of 5-Trifluoromethyl Pyrazoles by the [1+4] Cyclization of Phenylhydrazones with N-Aryl Trifluoroacetimidoyl Iodides

Hong-Bin Yu, Wei-Yuan Huang*
  • *Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, 200032, Shanghai, China, Fax 0086-21 64166128; E-mail: wyhuang@pub.sioc.ac.cn
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Publication Date:
31 December 2000 (online)

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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.

trifluoromethyl - pyrazole - [1+4] cyclization - N-aryl trifluoroacetimidoyl iodide