Transition-Metal-Mediated Three-Component Cascade Cyclization: Selective Cage B–C(sp²) Coupling of Carborane with Aromatics and Synthesis of Carborane-Fused Tricyclics

Zirconium/nickel comediated one-pot three-component cascade cyclization of carboryne, alkene, and 2-bromophenyltrimethylsilylacetylene has been achieved, leading to the formation of a series of C,C,B-substituted carborane-fused tricyclics. On the basis of experimental results, a plausible mechanism is proposed including [2 + 2 + 1] cross-cyclotrimerization followed by intramolecular direct selective cage B–C­(sp2) coupling. This represents the first example of direct cage B–C­(phenyl) coupling via cage B–H activation.