Pd-Catalyzed Sequential B(3)-I/B(4)-H Bond Activation For The Synthesis Of 3,4-Benzo-O-Carboranes

A palladium-catalyzed sequential B(3)-I and B(4)-H bond activation has been achieved for the synthesis of 3,4-benzo-o-carboranes via a formal [2 + 2 + 2] cycloaddition of 3-I-o-carborane with 2 equiv. of arylalkynes. This represents a new protocol to construct o-carborane-fused cyclics in one process, in which the Pd fragment migrates formally from the B(3) to B(4) position of the cage.