One-pot Annulation for Biaryl-fused Monocarba-closo-dodecaborate through Aromatic B−H Bond Disconnection

We have developed a one-pot annulation reaction of monocarba-closo-dodecaborate with cyclic diaryliodonium salts to afford biaryl-fused derivatives. Aryl functionalities are introduced at both the 1-carbon and unreactive ortho-boron vertices of the “σ-aromatic” carborane cage without the need for pre-functionalization. DFT calculations revealed that the palladium-catalyzed C−B bond-formation step in this process proceeds through a concerted metalation–deprotonation (CMD)-type pathway for the B−H bond disconnection on the aromatic cage, though such bonds are generally regarded as hydridic.