Iridium-Catalyzed Asymmetric Difunctionalization of C–C σ‑Bonds Enabled by Ring-Strained Boronate Complexes

Enantioenriched organoboron intermediates are important building blocks in organic synthesis and drug discovery. Recently, transition metal-catalyzed enantioselective 1,2-metalate rearrangements of alkenylboronates have emerged as an attractive protocol to access these valuable reagents by installin...

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Published in:Journal of the American Chemical Society 2023-08, Vol.145 (30), p.16508-16516
Main Authors: Shen, Hong-Cheng, Popescu, Mihai V., Wang, Ze-Shu, de Lescure, Louis, Noble, Adam, Paton, Robert S., Aggarwal, Varinder K.
Format: Article
Language:English
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Summary:Enantioenriched organoboron intermediates are important building blocks in organic synthesis and drug discovery. Recently, transition metal-catalyzed enantioselective 1,2-metalate rearrangements of alkenylboronates have emerged as an attractive protocol to access these valuable reagents by installing two different carbon fragments across CC π-bonds. Herein, we report the development of an iridium-catalyzed asymmetric allylation-induced 1,2-metalate rearrangement of bicyclo[1.1.0]­butyl (BCB) boronate complexes enabled by strain release, which allows asymmetric difunctionalization of C–C σ-bonds, including dicarbonation and carboboration. This protocol provides a variety of enantioenriched three-dimensional 1,1,3-trisubstituted cyclobutane products bearing a boronic ester that can be readily derivatized. Notably, the reaction gives trans diastereoisomers that result from an anti-addition across the C–C σ-bond, which is in contrast to the syn-additions observed for reactions promoted by PdII–aryl complexes and other electrophiles in our previous works. The diastereoselectivity has been rationalized based on a combination of experimental data and density functional theory calculations, which suggest that the BCB boronate complexes are highly nucleophilic and react via early transition states with low activation barriers.
ISSN:0002-7863
1520-5126
DOI:10.1021/jacs.3c03248