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Enantioselective Silicon-Directed Nazarov Cyclization.

Jin Cao¹, Meng-Yang Hu¹, Si-Yuan Liu¹

¹The State Key Laboratory and Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, China.

Journal of the American Chemical Society

|April 28, 2021

Summary

This study introduces a novel silicon-directed Nazarov reaction for synthesizing chiral cyclopentenones. This catalytic method offers a new route to complex molecules not accessible through other enantioselective reactions.

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Area of Science:

Organic Chemistry
Synthetic Chemistry

Background:

The Nazarov electrocyclization is a key reaction for cyclopentenone synthesis.
Existing catalytic asymmetric methods have limitations in product substituent patterns due to double bond positioning control.

Purpose of the Study:

To develop a novel, highly enantioselective silicon-directed Nazarov reaction.
To overcome limitations of previous methods and expand synthetic applications.

Main Methods:

Cooperative catalysis using a Lewis acid and a chiral Brønsted acid.
Utilizing silicon groups in dienone substrates to direct regioselectivity.
Mechanistic studies involving Lewis acid-Brønsted acid synergy and enol intermediate proton transfer.

Main Results:

Successful synthesis of chiral cyclopentenones with unique substitution patterns.
Achieved high enantioselectivity in the silicon-directed Nazarov reaction.
Demonstrated that the silicon group dictates double bond position by stabilizing a beta-carbocation intermediate.

Conclusions:

The developed silicon-directed Nazarov reaction provides access to valuable chiral cyclopentenones.
Cooperative Lewis and chiral Brønsted acid catalysis offers a synergistic activation pathway.
Enantioselectivity is primarily driven by chiral Brønsted acid-catalyzed proton transfer in the enol intermediate.