Propargyl Hydrazides: Synthesis and Conversion Into Pyrazoles Through Hydroamination

Authors

  • Prof. Dr. Mitsuhiro Yoshimatsu,

    Corresponding author
    1. Department of Chemistry, Faculty of Education, Gifu University, Yanagido 1-1, Gifu 501-1193 (Japan), Fax: (+81) 58-293-2251
    • Department of Chemistry, Faculty of Education, Gifu University, Yanagido 1-1, Gifu 501-1193 (Japan), Fax: (+81) 58-293-2251
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  • Katsuki Ohta,

    1. Department of Chemistry, Faculty of Education, Gifu University, Yanagido 1-1, Gifu 501-1193 (Japan), Fax: (+81) 58-293-2251
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  • Nami Takahashi

    1. Department of Chemistry, Faculty of Education, Gifu University, Yanagido 1-1, Gifu 501-1193 (Japan), Fax: (+81) 58-293-2251
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Abstract

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Pyrazoles direct: Propargyl alcohols undergo hydrazination when treated with p-tosyl hydrazide in the presence of catalytic amounts of either Sc(OTf)3 or La(OTf)3 (see scheme; Tf=trifluoromethanesulfonyl). Propargyl hydrazides are converted into either N-tosyl or N-H pyrazoles when treated with an acid or a base, respectively. The one-step acid-catalyzed hydrazination/cyclization of propargyl alcohols directly affords pyrazoles in high yields.

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