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Synthesis of a Borylborenium Ion via Direct Dehydrocoupling of Two B-H Bonds
Yizhao Huang1, Zhen Hua Li1, Huadong Wang1,2
1Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Songhu Road 2005, Shanghai200438, China.
Abstract:
Dehydrocoupling of hydroboranes provides a highly efficient method for the synthesis of diboron species. While this process generally proceeds in the presence of transition metals or Lewis bases, direct dehydrocoupling of two hydroboranes to form a B-B bond is still unknown. Herein, we report that an in situ-generated dihydroborenium ion can readily undergo dehydrocoupling with an intramolecular o-carboranyl moiety to afford a borylborenium ion. Theoretical studies demonstrate that this seemingly symmetry-forbidden process is enabled by Lewis acid-mediated umpolung of the B-H bond of o-carboranyl moiety. The resulting borylborenium ion is a powerful electrophilic borylation reagent and readily borylates a number of unactivated arenes, such as dihaloarenes, at room temperature.
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