Regioselective One-Step Synthesis of Pyrazoles from Alkynes and N-Tosylhydrazones: [3+2] Dipolar Cycloaddition/[1,5] Sigmatropic Rearrangement Cascade

Authors

  • M. Carmen Pérez-Aguilar,

    1. Instituto Universitario de Química Organometálica, “Enrique Moles”, Universidad de Oviedo c/Julián Clavería 8, Oviedo, 33006 (Spain)
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  • Dr. Carlos Valdés

    Corresponding author
    1. Instituto Universitario de Química Organometálica, “Enrique Moles”, Universidad de Oviedo c/Julián Clavería 8, Oviedo, 33006 (Spain)
    • Instituto Universitario de Química Organometálica, “Enrique Moles”, Universidad de Oviedo c/Julián Clavería 8, Oviedo, 33006 (Spain)

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  • Financial support of this work by the DGI of Spain (CTQ-2010-16790) and Consejería de Educación y Ciencia of Principado de Asturias (IB08-088). A FPI predoctoral fellowship to M.C.P.-A. is gratefully acknowledged.

Abstract

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Rearrangement under control: A wide variety of 3,4,5- and 1,3,5-trisubstituted pyrazoles can be prepared from tosylhydrazones of ketones and terminal alkynes through the title reaction sequence (see scheme; Ts=4-toluenesulfonyl). The rearrangement, and therefore, the regioselectivity of the reaction is controlled by the nature of the substituents of the tosylhydrazone.

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