Franta, Maximilian and Gramueller, Johannes and Dullinger, Philipp and Kaltenberger, Simon and Horinek, Dominik and Gschwind, Ruth M. (2023) Bronsted Acid Catalysis-Controlling the Competition between Monomeric versus Dimeric Reaction Pathways Enhances Stereoselectivities. ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 62 (27): e202301183. ISSN 1433-7851, 1521-3773
Full text not available from this repository. (Request a copy)Abstract
Chiral phosphoric acids (CPA) have become a privileged catalyst type in organocatalysis, but the selection of the optimum catalyst is still challenging. So far hidden competing reaction pathways may limit the maximum stereoselectivities and the potential of prediction models. In CPA-catalyzed transfer hydrogenation of imines, we identified for many systems two reaction pathways with inverse stereoselectivity, featuring as active catalyst either one CPA or a hydrogen bond bridged dimer. NMR measurements and DFT calculations revealed the dimeric intermediate and a stronger substrate activation via cooperativity. Both pathways are separable: Low temperatures and high catalysts loadings favor the dimeric pathway (ee up to -98 %), while low temperatures with reduced catalyst loading favor the monomeric pathway and give significantly enhanced ee (92-99 % ee; prior 68-86 % at higher temperatures). Thus, a broad impact is expected on CPA catalysis regarding reaction optimization and prediction.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | ASYMMETRIC TRANSFER HYDROGENATION; 1,3-DIPOLAR CYCLOADDITION; IMINES; 3,3'-SUBSTITUENTS; ORGANOCATALYSIS; ACTIVATION; REDUCTION; MECHANISM; DESIGN; MODEL; Chiral Phosphoric Acids; Enantioselectivity; Ion Pair Catalysis; NMR; Reaction Mechanism |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Organische Chemie > Arbeitskreis Prof. Dr. Ruth Gschwind Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry VI - Physical Chemistry (Solution Chemistry) > Prof. Dr. Dominik Horinek |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 01 Mar 2024 06:03 |
| Last Modified: | 01 Mar 2024 06:03 |
| URI: | https://pred.uni-regensburg.de/id/eprint/59213 |
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