Gold-catalyzed three-component spirocyclization: a one-pot approach to functionalized pyrazolidines
Bernd Wagner1, Wolf Hiller1, Hiroaki Ohno2
1Organic Chemistry, Dortmund University of Technology, Otto-Hahn-Str. 6, D-44227 Dortmund, Germany. norbert.krause@tu-dortmund.de.
Abstract:
An efficient, highly atom economic synthesis of hitherto unknown spirocyclic pyrazolidines in a one-pot process was developed. The gold-catalyzed three-component coupling of alkynols, hydrazines and aldehydes or ketones likely proceeds via cycloisomerization of the alkynol to an exocyclic enol ether and subsequent [3 + 2]-cycloaddition of an azomethine ylide. A library of 29 derivatives with a wide range of functional groups was synthesized in up to 97% yield. With this new method, every position in the final product can be substituted which renders the method ideal for applications in combinatorial or medicinal chemistry.
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