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Development of Heterogeneous Enantioselective Catalysts using Chiral Metal-Organic Frameworks MOFs
Published on: January 17, 2020
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Aggregation-Induced Catalysis: Asymmetric Catalysis with Chiral Aggregates
Yao Tang1, Yu Wang2, Qingkai Yuan1
1Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA.
Research (Washington, D.C.)
|June 12, 2023
Summary
Researchers developed a novel asymmetric catalysis method using chiral aggregates, enhancing enantioselectivity in reactions like olefin dihydroxylation. This aggregation-induced emission strategy offers a new pathway for chiral control in catalysis.
Area of Science:
- Organic Chemistry
- Catalysis
- Supramolecular Chemistry
Background:
- Traditional methods for controlling chirality include chiral auxiliaries, reagents, solvents, and catalysts, with asymmetric catalysts typically categorized as homogeneous or heterogeneous.
- A gap exists in the literature for asymmetric control strategies beyond these established classifications.
Purpose of the Study:
- To introduce a novel asymmetric catalysis strategy based on chiral aggregates.
- To demonstrate the efficacy of this new approach in catalytic asymmetric dihydroxylation reactions.
- To explore the potential for extending this strategy to other asymmetric reactions.
Main Methods:
- Utilizing aggregation-induced emission systems with tetrahydrofuran and H2O cosolvents to aggregate chiral ligands.
- Investigating the impact of cosolvent ratios on enantioselectivity (er).
- Employing aggregation-induced emission and aggregation-induced polarization to confirm the formation of chiral aggregates.
- Exploring methods to induce chiral aggregate formation, including salt addition and concentration changes.
Main Results:
- Achieved significant enhancement in enantioselectivity, improving er from 78:22 to 97:3 in olefin dihydroxylation by adjusting cosolvent ratios.
- Confirmed the formation of chiral aggregates of (DHQD)2PHAL and (DHQ)2PHAL ligands using aggregation-induced emission and polarization techniques.
- Demonstrated that chiral aggregates can be formed by adding NaCl or increasing ligand concentrations.
- Showcased promising reverse control of enantioselectivity in the Diels-Alder reaction.
Conclusions:
- A new paradigm for asymmetric catalysis via chiral aggregates has been established, distinct from homogeneous and heterogeneous approaches.
- The strategy offers tunable control over enantioselectivity, as evidenced by the dihydroxylation and Diels-Alder reactions.
- This aggregation-based approach holds broad potential for future applications in general and asymmetric catalysis.
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