Mechanistic basis for high reactivity of (salen)Co-OTs in the hydrolytic kinetic resolution of terminal epoxides
| Autor: | Lars P. C. Nielsen, Stephan J. Zuend, David D. Ford, Eric N. Jacobsen |
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| Rok vydání: | 2012 |
| Předmět: |
inorganic chemicals
chemistry.chemical_classification Molecular Structure Hydrolysis Organic Chemistry Epoxide Cobalt Ethylenediamines Article Catalysis Kinetic resolution chemistry.chemical_compound Kinetics chemistry Nucleophile Metal salen complexes Polymer chemistry Organometallic Compounds Organic chemistry Epoxy Compounds Reactivity (chemistry) Counterion Bimetallic strip |
| Zdroj: | The Journal of organic chemistry. 77(5) |
| ISSN: | 1520-6904 |
| Popis: | The (salen)Co(III)-catalyzed hydrolytic kinetic resolution (HKR) of terminal epoxides is a bimetallic process with a rate controlled by partitioning between a nucleophilic (salen)Co-OH catalyst and a Lewis acidic (salen)Co-X catalyst. The commonly used (salen)Co-OAc and (salen)Co-Cl precatalysts undergo complete and irreversible counterion addition to epoxide during the course of the epoxide hydrolysis reaction, resulting in quantitative formation of weakly Lewis acidic (salen)Co-OH and severely diminished reaction rates in the late stages of HKR reactions. In contrast, (salen)Co-OTs maintains high reactivity over the entire course of HKR reactions. We describe here an investigation of catalyst partitioning with different (salen)Co-X precatalysts and demonstrate that counterion addition to epoxide is reversible in the case of the (salen)Co-OTs. This reversible counterion addition results in stable partitioning between nucleophilic and Lewis acidic catalyst species, allowing highly efficient catalysis throughout the course of the HKR reaction. |
| Databáze: | OpenAIRE |
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