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γ-Trimethylsilylcyclobutyl carbocation stabilization
Xavier Creary1, Anna Heffron, Gabrielle Going
1Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States.
The Journal of Organic Chemistry
|January 7, 2015
Summary
The trimethylsilyl group significantly stabilizes arylcyclobutyl carbocations through rear lobe interaction, especially with electron-withdrawing aryl substituents. Front lobe interactions show minimal stabilization effects.
Area of Science:
- Organic Chemistry
- Physical Chemistry
- Computational Chemistry
Background:
- Carbocation stability is influenced by neighboring group participation.
- Silicon-containing groups can potentially stabilize adjacent cationic centers.
Purpose of the Study:
- To investigate the stabilizing effect of a 3-trimethylsilyl group on 1-arylcyclobutyl carbocations.
- To differentiate between rear lobe and front lobe interactions of the trimethylsilyl group with the carbocation.
Main Methods:
- Generation of isomeric 3-trimethylsilyl-1-arylcyclobutyl carbocations under solvolytic conditions.
- Kinetic studies to measure rate enhancements with varying aryl substituents.
- Computational studies to calculate stabilization energies.
Main Results:
- Solvolysis rate enhancements increased with electron-withdrawing aryl groups for rear lobe interactions.
- Minimal rate enhancement was observed for front lobe interactions.
- Computational studies corroborated solvolytic findings, showing increased stabilization with electron-withdrawing groups for rear lobe interactions.
Conclusions:
- Significant stabilization of arylcyclobutyl carbocations is provided by a 3-trimethylsilyl group via rear lobe interaction.
- Front lobe interaction of the trimethylsilyl group does not significantly stabilize these carbocations.
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