Catalytic, contra-Thermodynamic Positional Alkene Isomerization.
Gino Occhialini1, Vignesh Palani1, Alison E Wendlandt1
1Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Journal of the American Chemical Society
|December 30, 2021
Summary
This study introduces a novel dual catalyst system for contra-thermodynamic alkene isomerization, enabling direct synthesis of terminal alkenes from internal ones using photochemical irradiation.
Area of Science:
- Organic Chemistry
- Photochemistry
- Catalysis
Background:
- Positional isomerization of carbon-carbon double bonds (C═C) is crucial for interconverting alkene regioisomers.
- Current methods typically yield thermodynamically favored products, limiting synthetic flexibility.
Purpose of the Study:
- To develop a novel method for contra-thermodynamic positional alkene isomerization.
- To access terminal alkene isomers directly from conjugated internal alkene starting materials.
Main Methods:
- Utilized a dual catalyst system under photochemical irradiation.
- Investigated the deconjugation of electron-rich and electron-poor alkenes.
- Applied the method to natural product synthesis.
Main Results:
- Achieved contra-thermodynamic positional alkene isomerization.
- Successfully synthesized terminal alkene isomers from internal alkenes.
- Demonstrated broad utility with diverse alkene substrates and in natural product synthesis.
Conclusions:
- The discovered dual catalyst system enables unprecedented access to less stable alkene isomers.
- The reaction proceeds via a regiospecific bimolecular homolytic substitution (SH2') mechanism involving an allyl-cobaloxime intermediate.
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