Improving selectivity in catalytic hydrodefluorination by limiting SNV reactivity
Juliane Krüger1, Christian Ehm2, Dieter Lentz1
1Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstr. 34-36, 14195 Berlin, Germany. dieter.lentz@fu-berlin.de.
Dalton Transactions (Cambridge, England : 2003)
|October 26, 2016
Summary
Catalytic hydrodefluorination of perfluoroallylbenzene is unselective due to competing mechanisms. Using non-polar solvents increases selectivity in this important organofluorine reaction.
Area of Science:
- Organometallic Chemistry
- Fluorine Chemistry
- Computational Chemistry
Background:
- Catalytic hydrodefluorination is crucial for transforming fluorinated organic compounds.
- Perfluorinated olefins present unique reactivity challenges.
- Understanding reaction mechanisms is key to controlling selectivity.
Purpose of the Study:
- To investigate the mechanisms of catalytic hydrodefluorination of perfluoroallylbenzene.
- To identify factors influencing selectivity in this reaction.
- To explore computational and experimental approaches for mechanistic elucidation.
Main Methods:
- Density Functional Theory (DFT) calculations (M06-2X) with solvent correction (THF).
- Investigation of multiple reaction pathways: SET, hydrometallation/fluoride elimination, σ-bond metathesis, and SNV.
- Experimental validation of proposed mechanisms.
Main Results:
- Hydrodefluorination with Cp2TiH in THF is unselective, yielding various unknown compounds.
- Nucleophilic vinylic substitution (SNV) is a competitive pathway alongside hydrometallation.
- SNV proceeds via ionic intermediates, leading to facile and unselective fluoride elimination in polar solvents.
- Selectivity can be significantly enhanced by employing non-polar solvents.
Conclusions:
- The unselective nature of this reaction in polar solvents is attributed to competing mechanisms, particularly SNV.
- Solvent polarity plays a critical role in controlling the selectivity of hydrodefluorination.
- Optimizing solvent choice offers a viable strategy to improve selectivity in organofluorine transformations.
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