An Isolated Lithium ortho-Carboranyl Cuprate Complex for the Synthesis of Multiple-Carborane-Substituted Arenes from (Hetero)Aryl Bromides and Chlorides

Carborane-substituted arenes have emerged as versatile building blocks in medicinal chemistry, materials science, and coordination chemistry owing to the unique three-dimensional aromaticity, exceptional stability, and bioisosteric properties of carboranes. However, the existing synthetic routes to carborane-substituted arenes via C-C bond formation often rely on complex and laborious in situ procedures using aryl iodides, thus severely limiting the scope of their practical applications. Here, we report the isolation and characterization of a lithium bis(o-carboran-1-yl)cuprate complex (Li/Cu-1) that enables the efficient "dump-and-stir" synthesis of carborane-substituted arenes from readily available aryl bromides and chlorides. Remarkably, isophthalonitrile functions as a ligand for the Li center in Li/Cu-1, leaving the Cu center available for the oxidative addition to aryl halides. This represents a paradigm shift from traditional approaches using pyridines as ligands for Cu centers. Our method provides access to a diverse array of unprecedented molecules, including multiple-carborane-substituted or carborane-fused arenes, thereby converting a hitherto difficult transformation in synthetic chemistry into a practical and scalable process.