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Highly selective copper-catalyzed hydroboration of allenes and 1,3-dienes
Kazuhiko Semba1, Masataka Shinomiya, Tetsuaki Fujihara
1Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
Abstract:
The highly selective copper-catalyzed hydroboration of allenes has been developed. Allylboranes and alkenylboranes were selectively prepared by the judicious choice of catalytic species (copper hydride and boryl copper). Furthermore, two types of alkenylboranes could be selectively synthesized by the choice of an appropriate ligand. Mechanistic studies confirmed that the protonation of a (Z)-σ-allyl copper species, which was isolated and structurally characterized by single-crystal X-ray diffraction, was a key step in these reactions. Besides allenes, this method is also applicable to the selective hydroboration of 1,3-diene derivatives to afford allylboranes and homoallylboranes.
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