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Published on: November 15, 2017
Trisubstituted geminal diazaalkene derived transient 1,2-carbodications
Debdeep Mandal1, Felix Stein, Shubhadeep Chandra
1Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500107, Telangana, India. ajana@tifrh.res.in.
Transient 1,2-carbodications with a hydrogen substituent exhibit reduced charge repulsion through intramolecular base-coordination. This study explores charge delocalization in these novel carbocation species using N-heterocyclic olefins.
Area of Science:
- Organic Chemistry
- Computational Chemistry
- Spectroscopy
Background:
- Coulombic repulsion in 1,2-carbodications typically decreases with electron-donating substituents.
- Charge delocalization is a key factor in stabilizing carbocationic species.
Purpose of the Study:
- To investigate the delocalization of positive charge in transient 1,2-carbodications with a single hydrogen substituent.
- To explore the role of intramolecular base-coordination in stabilizing these carbocations.
- To synthesize and characterize novel N-heterocyclic olefin (NHO) derived precursors.
Main Methods:
- Generation of transient 1,2-carbodications via a two-electron chemical oxidation process.
- Synthesis of N-heterocyclic olefin (NHO) derived 2-pyrrolidinyl appended trisubstituted geminal diazaalkenes.
- Electrochemical and chemical one-electron oxidation studies.
- In situ Electron Paramagnetic Resonance (EPR) spectroscopy.
Main Results:
- Demonstrated charge delocalization in 1,2-carbodications with a hydrogen substituent through intramolecular base-coordination.
- Successfully generated transient 1,2-carbodications using the designed NHO precursors.
- Characterized the oxidation reactions and electronic properties of the geminal diazaalkenes.
Conclusions:
- Intramolecular base-coordination effectively delocalizes positive charge in 1,2-carbodications, even with a hydrogen substituent.
- NHO-derived geminal diazaalkenes are effective precursors for generating and studying transient carbocations.
- The findings provide new insights into the stabilization mechanisms of carbocationic species.
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