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Improved Synthesis of Icosahedral Carboranes Containing Exohedral B–c and C–c Bonds

preprint
submitted on 25.10.2018 and posted on 26.10.2018 by Kierstyn P. Anderson, Harrison A. Mills, Chantel Mao, Kent O. Kirlikovali, Jonathan C. Axtell, Arnold L. Rheingold, Alexander Spokoyny

We report improved methods utilizing orthogonal chemistry to achieve efficient substitution at electron-rich B-vertices and electron-poor C-vertices of carborane. Functionalization of B-vertices with alkyl and (hetero)aryl groups using corresponding Grignard reagents has been improved by the use of a Pd-based precatalyst featuring an electron-rich biaryl phosphine ligand. Using the developed catalytic conditions lead to cross-coupling transformations achieved within several hours. Importantly, this method is applicable towards alkyl-based Grignard reagents containing β-hydrogens. Additionally, transition metal-free substitution of (hetero)aryl substrates on C-vertices was developed under SNAr conditions. The selective substitution of carboranes afforded by these methods holds potential for the rational synthesis of heterofunctionalized boron clusters with substituents on both boron and carbon-based vertices.

Funding

National Institutes of Health (NIH), Maximizing Investigators Research Award (MIRA, R35GM124746)

History

Email Address of Submitting Author

spokoyny@chem.ucla.edu

Institution

UCLA

Country

USA

ORCID For Submitting Author

0000-0002-5683-6240

Declaration of Conflict of Interest

Authors declare no conflict of interests.

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