Borenium Ylide-Mediated 12-B Arylation of Carborane Anions.

Developing novel approaches for B-vertex modification is significant in the chemistry of icosahedral boron clusters. Here, we report a protocol for the transformation of air-stable 12-aryliodonium carborane anions, which are readily accessible on a gram scale from the corresponding (diacetoxyiodo)arenes (ArI(OAc)) and carborane anion, to 12-aryl-carborane anions. Mechanistic studies support the idea that the 12-B arylation proceeds via intramolecular reductive C-B bond formation on the carborane 12-borenium ylide, followed by rearomatization. The reaction proceeds under mild conditions in air and is suitable for one-pot synthesis without the need for purification of the 12-aryliodonium carborane anions. B-B coupling reaction at the 12-B vertex affords dumbbell-type carborane anion dimers. This reaction offers an alternative approach for B-C bond formation in borates, complementing conventional cross-coupling approaches.