Electrochemical Synthesis of Boron-Centered Carboranyl Radical for Modular Carboranyl N-Heterocycles

Carboranes, three-dimensional boron-rich bioisosteres of phenyl rings, have emerged as promising scaffolds in small-molecule drug discovery owing to their unique 3D architecture, excellent metabolic stability, and abundant hydrogen-bonding recognition sites. The methods for the efficient synthesis of carborane-containing heterocyclic scaffolds are, however, limited. To address this challenge, we report herein a modular synthetic platform for the systematic construction of a series of carboranyl N-heterocycles. This platform relies on the metal-free electrochemical generation of boron-centered radicals via the reductive activation of B-N bonds followed by radical cascade cyclization with ortho-acceptor-substituted aryl isocyanides at room temperature. The protocol employs an undivided electrolysis cell with low-cost carbon-based electrodes and exhibits a high reaction efficiency. Furthermore, late-stage functionalization of the resulting carborano-heterocycles is feasible via derivatization of cage CH vertex sites and Suzuki-Miyaura coupling reactions. Characterized by mild reaction conditions, rapid conversion rates, a broad substrate scope, and excellent functional group tolerance, this transformation harbors key attributes rendering the method potentially applicable for the development of boron-cluster-modified pharmaceutical agents. Radical trapping experiments confirm the involvement of boron-centered radicals in the reaction mechanism. This method also provides a valuable reference for generating boron or other main-group-element-centered radicals using electrochemical strategies.