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Regioselective and Enantioselective Intermolecular Buchner Ring Expansions in Flow
Gabrielle S Fleming1, Aaron B Beeler1
1Department of Chemistry, Boston University , 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States.
Organic Letters
|September 12, 2017
Summary
Continuous flow chemistry enables the first regioselective and enantioselective intermolecular Buchner ring expansion. This method efficiently synthesizes cycloheptatrienes with improved practicality and scope.
Area of Science:
- Organic Chemistry
- Synthetic Chemistry
- Flow Chemistry
Background:
- The Buchner reaction is a classical method for synthesizing cycloheptatrienes.
- Traditional Buchner reactions often suffer from limited scope and regioselectivity issues.
- Developing enantioselective variants remains a significant challenge in synthetic organic chemistry.
Purpose of the Study:
- To report the first example of a regioselective and enantioselective intermolecular Buchner ring expansion.
- To demonstrate the advantages of using continuous flow technology for this transformation.
- To explore the scope and efficiency of the developed method.
Main Methods:
- Utilized continuous flow reactor systems for the Buchner ring expansion.
- Employed ethyl diazoacetate and various arenes as starting materials.
- Developed an asymmetric variant using disubstituted diazo esters to achieve enantioselectivity.
Main Results:
- Achieved good yields and excellent regioselectivity in the synthesis of cycloheptatrienes from symmetric and nonsymmetric arenes.
- Demonstrated the first asymmetric intermolecular Buchner reaction with good to excellent enantioselectivity.
- Confirmed absolute regioselectivity in asymmetric reactions, yielding cycloheptatrienes with an all-carbon quaternary center.
Conclusions:
- Continuous flow conditions significantly improve the practicality and scope of the intermolecular Buchner reaction.
- The developed method provides efficient access to substituted cycloheptatrienes with high regio- and enantiocontrol.
- This work represents a significant advancement in asymmetric catalysis and synthetic methodology.
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