Palladium-Catalyzed Direct Dialkenylation of Cage BH 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, -H elimination, reductive elimination, and decarboxylation.