Transition Metal Catalyzed, Regioselective B(4)-Halogenation and B(4,5)-Diiodination of Cage B-H Bonds in o-Carboranes

Transition metal catalyzed, regioselective carborane-cage B(4)-H iodination, bromination, and chlorination as well as B(4,5)-H diiodination were achieved by using NXS (X=I, Br), FeCl3, or IOAc as the halogenating agent, respectively. A series of previously inaccessible B(4)-halogenated o-carboranes were synthesized in a simple one-pot process, and proved to be valuable synthons for the functionalization of carboranes. Mono- and di-selectivity can be controlled by in situ removal of the carboxy directing group. The resultant 4-I-o-C2B10H11 can serve as a versatile feedstock for the construction of cage B-C(sp(2)), B-C(sp), B-O, and B-N bonds.