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Synthesis 1991; 1991(12): 1153-1156
DOI: 10.1055/s-1991-28409
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Ring Transformation by Ring Chain Transfer VI1: Regioselective Synthesis of (ω-Aminoalkyl)pyrazoles from Semicyclic 3-Chloro-2-propeniminium Salts and Hydrazines

Jörg Bohrisch* , Michael Pätzel, C. Mügge, Jürgen Liebscher
  • *Fachbereich Chemie, Humboldt-Universität Berlin, D-1040 Berlin, Hessische Str. 1-2, Germany
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Publication Date:
29 April 2002 (online)

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Novel semicyclic 3-aryl-3-chloro-2-propeniminium perchlorates 6 are synthesized by treating semicyclic enaminones 1 (2-aroylmethylene-1-methylpyrrolidines, -piperidines and -azepanes) with phosphoryl chloride dimethylformamide. Reaction of these chloropropeniminium salts 6 with hydrazines 2 give regiospecifically either 3-(ω-aminoalkyl)- or 5-(ω-aminoalkyl)pyrazoles 5 or 10. The direction of these ring transformation reactions is governed by the nature of substituent of the hydrazine. The synthesis is especially useful in the preparation of 1-substituted 5-(ω-aminoalkyl)pyrazoles 10.

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