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Boron-Enabled Geometric Isomerization of Small Alkene Fragments via Selective Energy Transfer Catalysis

preprint
submitted on 13.03.2020 and posted on 16.03.2020 by John James Molloy, Michael Schäfers, Max Wienhold, Tobias Morack, Constantin G. Daniliuc, Ryan Gilmour
The mammalian visual cycle epitomizes the importance of complex polyenes in biology. However, isomerization-based strategies to enable the sterodivergent construction of these important biomolecules from geometrically defined alkene linchpins remain conspicuously underdeveloped. Mitigating the thermodynamic constraints inherent to isomerization is further frustrated by the considerations of atom efficiency in idealized low molecular precursors. Herein, we report a general ambiphilic C3 scaffold that can be isomerized and bi-directionally extended. Predicated on highly efficient triplet energy transfer, the selective isomerization of β-15 borylacrylates is contingent on the participation of the boron p-orbital in the substrate chromophore. Rotation of the C(sp2)-B bond by 90° in the product renders re-excitation inefficient and endows directionality. This subtle stereoelectronic gating mechanism enables the stereocontrolled syntheses of well-defined retinoic acid derivatives.

Funding

Deutsche Forschungsgemeinschaft

Alexander von Humboldt Foundation

History

Email Address of Submitting Author

ryan.gilmour@uni-muenster.de

Institution

Westfälische Wilhelms-Universität Münster

Country

Germany

ORCID For Submitting Author

0000-0002-3153-6065

Declaration of Conflict of Interest

No conflict of interest.

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