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Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
Transition-Metal-Free Self-Hydrogen-Transferring Allylic Isomerization
Hong-Xing Zheng1, Zu-Feng Xiao1, Chuan-Zhi Yao1
1Center of Advanced Nanocatalysis, Department of Chemistry, University of Science and Technology of China , Hefei, Anhui 230026, China.
This study introduces a new transition-metal-free method for allylic isomerization using phenanthroline and tert-butoxide as radical initiators. This process generates key ketone intermediates for indene synthesis, proceeding via a radical pathway.
Area of Science:
- Organic Chemistry
- Catalysis
- Radical Reactions
Background:
- Phenanthroline and tert-butoxide are known radical initiators.
- These initiators are effective in SRN1-type coupling reactions.
- Their cooperative effect stems from heteroarene structure and tert-butoxide properties.
Purpose of the Study:
- To describe the first phenanthroline-tert-butoxide-catalyzed transition-metal-free allylic isomerization.
- To demonstrate the generation of ketone intermediates crucial for indene synthesis.
Main Methods:
- Catalysis using phenanthroline and tert-butoxide.
- Control experiments to exclude alternative pathways.
- Detailed mechanistic investigations including kinetic studies, kinetic isotope effect, isotope-labeling, trapping experiments, and electron paramagnetic resonance (EPR) spectroscopy.
Main Results:
- Successful transition-metal-free allylic isomerization catalyzed by phenanthroline-tert-butoxide.
- Formation of ketone intermediates essential for synthesizing indenes.
- Experimental evidence strongly supports a radical pathway, ruling out a base-promoted allylic anion mechanism.
Conclusions:
- Phenanthroline-tert-butoxide is an effective catalytic system for transition-metal-free allylic isomerization.
- The reaction proceeds via a radical mechanism, offering a novel synthetic route to indene precursors.
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