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Cooperative Stereoinduction in Asymmetric Photocatalysis.
Steven J Chapman1, Wesley B Swords1, Christine M Le2
1Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53703, United States.
Journal of the American Chemical Society
|February 22, 2022
Summary
Researchers developed a new tandem chiral photocatalyst/Brønsted acid strategy for enantioselective photocycloadditions. Matched and mismatched catalyst pairs showed cooperative excited-state effects, influencing reaction rates and selectivity in organic synthesis.
Area of Science:
- Organic Chemistry
- Photochemistry
- Stereoselective Synthesis
Background:
- Cooperative effects from multiple stereocontrol elements are key in ground-state organic reactions.
- Controlling photochemical reactions with high stereoselectivity is a recent challenge.
- Cooperative stereocontrolling effects in excited-state photoreactions remain largely undocumented.
Purpose of the Study:
- To develop a novel strategy for highly enantioselective photochemical reactions.
- To investigate cooperative stereocontrolling effects in excited-state dual-catalysis.
- To explore the influence of matched/mismatched chiral catalysts in photoreactions.
Main Methods:
- Employed a tandem chiral photocatalyst and Brønsted acid system.
- Utilized [2 + 2] photocycloadditions of vinylpyridines.
- Analyzed reaction rates and enantioselectivities with varying chiral catalyst pairs and coupling partners.
Main Results:
- Achieved highly enantioselective [2 + 2] photocycloadditions of vinylpyridines.
- Observed distinct reaction rates and enantioselectivities for matched versus mismatched catalyst pairs.
- Confirmed that cooperative effects arise from excited-state interactions, not ground-state ones.
Conclusions:
- The developed tandem strategy enables highly enantioselective photocycloadditions.
- Cooperative matched/mismatched effects in excited-state photoreactions are demonstrated for the first time.
- These findings suggest broader applicability of cooperative stereocontrol in dual-catalytic photochemistry.
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