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Updated: Aug 7, 2026

Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
Mechanisms of allene stereoinversion by imidozirconium complexes
Forrest E Michael1, Andrew P Duncan, Zachary K Sweeney
1Department of Chemistry and Center for New Directions in Organic Synthesis, University of California at Berkeley, Berkeley, California 94720, USA.
Abstract:
The zirconium-mediated stereoinversion of allenes has been investigated by studying the stereochemical behavior of metallacycles derived from [2 + 2] cycloaddition of enantioenriched allenes with chiral and achiral imidozirconocene complexes. Relative rates of metallacycle racemization were measured by circular dichroism, and intermediates in the selective stereoinversion of diphenylallene with a chiral imidozirconium complex were observed by NMR spectroscopy. Metallacycles derived from dialkylallenes are proposed to racemize via reversible beta-hydride elimination. Stereoinversion of diarylallene-derived metallacycles proceeds much more slowly and is thought to proceed through an eta4-azatrimethylenemethane transition state.
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