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J Am Chem Soc. 2018 Oct 24;140(42):13798-13807. doi: 10.1021/jacs.8b07872. Epub 2018 Oct 1.

Palladium-Catalyzed Selective Five-Fold Cascade Arylation of the 12-Vertex Monocarborane Anion by B-H Activation.

Author information

1
Department of Chemistry , Zhejiang University , 38 Zheda Road , 310027 Hangzhou , People's Republic of China.
2
Department of Chemistry , University of Zurich , Winterthurerstrasse 190 , 8057 Zurich , Switzerland.

Abstract

A series of cage penta-arylated carboranes have been synthesized by palladium-catalyzed intermolecular coupling of the C-carboxylic acid of the monocarba- closo-dodecaborate anion [CB11H12]- with iodoarenes by direct cage B-H bond functionalization. These transformations set a record in terms of one-pot directing group-mediated activation of inert bonds in a single molecule. The methodology is characterized by high yields, good functional group tolerance, and complete cage regioselectivity. The directing group COOH can be easily removed during or after the intermolecular coupling reaction. The mechanistic pathways were probed using density functional theory calculations. A Pd(II)-Pd(IV)-Pd(II) catalytic cycle is proposed, in which initial coupling is followed by preferred B-H activation of the adjacent boron vertex, and continuation of this selectivity results in a continuous walking process of the palladium center. The methodology opens a new avenue toward building blocks with 5-fold symmetry.

PMID:
30231610
DOI:
10.1021/jacs.8b07872

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