Palladium‐Catalyzed Direct Dialkenylation of Cage BH Bonds in o ‐Carboranes through Cross‐Coupling Reactions

Palladium‐catalyzed direct dialkenylation of cage B(4,5)H bonds in o ‐carboranes has been achieved with the help of a carboxylic acid directing group, leading to the preparation of a series of 4,5‐[trans‐(ArCHCH)] 2 ‐ocarboranes in high yields with excellent regioselectivity. The traceless directing group, eliminated during the course of the reaction, is responsible for controlling regioselectivity and dialkenylation. A possible catalytic cycle is proposed, involving a tandem sequence of Pd II ‐initiated cage BH activation, alkene insertion, β‐H elimination, reductive elimination, and decarboxylation.