Gold-catalyzed three-component spirocyclization: a one-pot approach to functionalized pyrazolidines†
Bernd Wagner,Wolf Hiller,Hiroaki Ohno,Norbert Krause
Organic & Biomolecular Chemistry Pub Date : 12/15/2015 00:00:00 , DOI:10.1039/C5OB02453F
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.

Graphical abstract: Gold-catalyzed three-component spirocyclization: a one-pot approach to functionalized pyrazolidines