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Enantioselective Conjugate Addition of Catalytically Generated Zinc Homoenolate

preprint
submitted on 19.01.2021, 15:43 and posted on 20.01.2021, 13:17 by Yoshiya Sekiguchi, Naohiko Yoshikai

We report herein an enantioselective conjugate addition reaction of a zinc homoenolate, catalytically generated via ring opening of a cyclopropanol, to an α,β-unsaturated ketone. The reaction is promoted by a zinc aminoalkoxide catalyst generated from Et2Zn and a chiral β-amino alcohol to afford 1,6- diketones, which undergo, upon heating, intramolecular aldol condensation to furnish highly substituted cyclopentene derivatives with good to high enantioselectivities. The reaction has proved applicable to various 1-substituted cyclopropanols as well as chalcones and related enones. The chiral amino alcohol has proved to enable ligand-accelerated catalysis of the homoenolate generation and its conjugate addition. Positive nonlinear effects and lower reactivity of a racemic catalyst have been observed, which can be attributed to a stable and inactive heterochiral zinc aminoalkoxide dimer.

Funding

Singapore Ministry of Education, MOE2016-T2-2-043

Singapore Ministry of Education, RG101/19

History

Email Address of Submitting Author

nyoshikai@ntu.edu.sg

Institution

Nanyang Technological University

Country

Singapore

ORCID For Submitting Author

0000-0002-8997-3268

Declaration of Conflict of Interest

The authors declare no competing financial interests.

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