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Synthesis 1995; 1995(5): 577-581
DOI: 10.1055/s-1995-3958
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Syntheses of Formazans Under Phase-Transfer Conditions

Alan A. Katritzky* , Sergei A. Belyakov, Dai Cheng, H. Dupont Durst
  • *Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville FL 32611-7200, USA
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Publication Date:
31 December 2000 (online)

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Several 1,3,5-triarylformazans were synthesized (42-77%) using a new methodology. Azo-coupling of aryldiazonium salts with arylaldehyde arylhydrazones under mild basic conditions in two-phase liquid-liquid media is efficiently promoted by phase-transfer catalysts (onium salts or dicyclohexano-18-crown-6) at 5-25°C. The condensation of benzaldehyde with phenylhydrazine followed by phase-transfer catalyzed azo-coupling with phenyldiazonium chloride (one-pot procedure) gave 1,3,5-triphenylformazan in a 54% yield without isolation of the intermediate benzaldehyde phenylhydrazone. A double azo-coupling reaction of phenyldiazonium chloride with 9 different CH-active compounds afforded corresponding formazan only in the case of phenylpyruvic acid. Reaction in malonamide gave 3-carbamoyl-1,5-diphenylformazan instead of the expected 1,5-diphenylformazan.

formazans - synthesis - phase-transfer catalysis - tetrabutylammonium salts - dicyclohexano-18-crown-6