Expanding the Scope of Palladium-Catalyzed B–N Cross-Coupling Chemistry in Carboranes

Abstract

Over the past several years, a number of strategies for the functionalization of dicarba-<i>closo</i>-dodecaboranes (carboranes) have emerged. Despite these developments, B - N bond formation on the carborane scaffold remains a challenge due to the propensity of strong nucleophiles to partially deboronate the parent <i>closo</i>-carborane cluster into the corresponding <i>nido</i> form. Here we show that azide, sulfonamide, cyanate, and phosphoramidate nucleophiles can be straightforwardly cross-coupled onto the B(9) vertices of the <i>o</i>- and <i>m</i>-carborane core from readily accessible precursors without significant deboronation by-products, laying the groundwork for further study into the utility and properties of these new B-aminated carborane species. We further showcase select reactivity of the installed functional groups highlighting some unique features stemming from the combination of the electron-donating B(9) position and the large steric profile of the B-connected carborane substituent.