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Ring closing enyne metathesis: control over mode selectivity and stereoselectivity.
1Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, USA.
Journal of the American Chemical Society
|November 19, 2004
Summary
Ring closing enyne metathesis efficiently forms macrocycles. Ethylene atmosphere improves selectivity for endo-products and E/Z isomers in macrocyclic dienes.
Area of Science:
- Organic Chemistry
- Catalysis
- Synthetic Chemistry
Background:
- Ring closing enyne metathesis is a powerful tool for macrocycle synthesis.
- Controlling selectivity in macrocyclization remains a challenge.
Purpose of the Study:
- To develop a selective method for synthesizing 10-15-membered rings via ring closing enyne metathesis.
- To investigate the factors influencing exo/endo and E/Z selectivity.
Main Methods:
- Utilized tartrate-derived linkers to connect ene and yne subunits.
- Performed ring closing enyne metathesis reactions under varying conditions, including ethylene atmosphere.
- Analyzed product selectivity based on ring size and reaction conditions.
Main Results:
- Ring size dictates exo/endo selectivity: larger rings (12-15) favor endo, smaller rings (5-11) favor exo.
- Ethylene atmosphere significantly improves both exo/endo selectivity and E/Z selectivity of macrocyclic dienes.
- Ethylene induces cross metathesis, leading to diene metathesis that exclusively forms endo-products with high E-selectivity.
Conclusions:
- Ring closing enyne metathesis is a viable route to macrocycles.
- Ethylene atmosphere is crucial for achieving high selectivity in macrocyclization via this method.
- The described method offers precise control over macrocyclic diene synthesis.
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