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Coarctate and Pseudocoarctate Reactions: Stereochemical Rules.
1Institut für Organische Chemie, Kiel University , Otto-Hahn-Platz 4, 24118 Kiel, Germany.
The Journal of Organic Chemistry
|October 1, 2015
Summary
Coarctate reactions are a unique type of concerted reaction where two bonds form and break simultaneously in the transition state. Electron counts and "coarctate rules" help predict their reactivity and stereochemistry, unlike pseudocoarctate states.
Area of Science:
- Organic Chemistry
- Reaction Mechanisms
- Theoretical Chemistry
Background:
- Concerted reactions involve simultaneous bond breaking and formation.
- Existing classes include S(N)2, E2, and pericyclic reactions.
- Coarctate reactions represent a distinct, previously unclassified category.
Purpose of the Study:
- To define and characterize coarctate reactions.
- To differentiate coarctate reactions from other concerted reaction types.
- To establish predictive rules for coarctate reaction outcomes.
Main Methods:
- Analysis of transition state structures.
- Application of electron counting principles.
- Topological analysis of orbital overlap.
- Comparison with pericyclic reaction principles.
Main Results:
- Coarctate reactions involve simultaneous formation and breaking of two bonds in the transition state.
- Electron counts can predict reactivity and stereochemistry, similar to pericyclic reactions.
- "Coarctate rules" derived from topological aromaticity principles.
Conclusions:
- Coarctate reactions are a unique class of concerted reactions.
- The "coarctate rules" provide a framework for understanding their behavior.
- Pseudocoarctate transition states deviate from these rules due to topological disconnections.
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