2- Phenyl-5-substituted pyrazol-3-ones preparation

Hydrazones are also useful substrates in the preparation of pyrazoles. Reaction of N-monosubstituted hydrazones with nitroolefins led to a regioselective synthesis of substituted pyrazoles <060L3505>. lf/-3-Ferrocenyl-l-phenylpyrazole-4-carboxaldehyde was achieved by condensation of acetylferrocene with phenylhydrazine followed by intramolecular cyclization of the hydrazone obtained under Vilsmeier-Haack conditions <06SL2581>. A one-pot synthesis of oxime derivatives of l-phenyl-3-arylpyrazole-4-carboxaldehydes has been accomplished by the Vilsmeier-Haack reaction of acetophenone phenylhydrazones <06SC3479>. 

A convenient method to obtain 3-amino-5-trifluoromethyl-l//-pyrazoles by cyclocondensation of 4-amino-4-ethoxy-l,l,l-trifluorobut-3-en-2-ones with hydrazine and phenylhydrazine has been reported <2006SL1485>. Trifluoromethylated pyrazoles were synthesized from trifluoromethylenaminones and monosubstituted hydrazines <2004JFC(125)1299>. 5-Amino-3-phenylpyrazoles 534 were prepared from a-oxoketene 0,W-acetals 533 using montmor-illonite K-10 under sonication conditions (Equation 108) <200381160>. 3-Amino-l-(/)-phenyl-substituted)-2-buten-l-ones... 

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