Palladium-catalyzed B7–11 penta-arylation of the {CB11} monocarborane cluster

Abstract

Regioselective, five-fold B–H activation of the monocarborane cluster [CB₁₁H₁₂]⁻ at the positions B7–11 has been accomplished. Selective substitution of these positions by B–H activation has not been reported before. Our protocol involves directing group assistance by the carboxylic acid functionality and is based on palladium catalysis using iodoarene coupling partners. Penta-arylated products are obtained in a single step with yields ranging from 42% to 89% and with good functional group tolerance. X-Ray crystal structures for five new compounds confirm the selective substitution of the lower belt of the monocarborane cage.