Cage-Walking: Vertex Differentiation by Palladium-Catalyzed Isomerization of B(9)-Bromo-meta-Carborane

We report the first observed Pd-catalyzed isomerization (“cage-walking”) of B(9)-bromo-meta-carborane during Pd-catalyzed cross-coupling, which enables the formation of B–O and B–N bonds at all boron vertices (B(2), B(4), B(5), and B(9)) of meta-carborane. Experimental and theoretical studies sugges...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2017-06, Vol.139 (23), p.7729-7732
Main Authors: Dziedzic, Rafal M, Martin, Joshua L, Axtell, Jonathan C, Saleh, Liban M. A, Ong, Ta-Chung, Yang, Yun-Fang, Messina, Marco S, Rheingold, Arnold L, Houk, K. N, Spokoyny, Alexander M
Format: Article
Language:English
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Summary:We report the first observed Pd-catalyzed isomerization (“cage-walking”) of B(9)-bromo-meta-carborane during Pd-catalyzed cross-coupling, which enables the formation of B–O and B–N bonds at all boron vertices (B(2), B(4), B(5), and B(9)) of meta-carborane. Experimental and theoretical studies suggest this isomerization mechanism is strongly influenced by the steric crowding at the Pd catalyst by either a biaryl phosphine ligand and/or substrate. Ultimately, this “cage-walking” process provides a unique pathway to preferentially introduce functional groups at the B(2) vertex using B(9)-bromo-meta-carborane as the sole starting material through substrate control.
ISSN:0002-7863
1520-5126
DOI:10.1021/jacs.7b04080