Metal-Free Oxidative B-N Coupling of nido-Carborane with N-Heterocycles.

A general method for the oxidative substitution of nido-carborane (7,8-C2 B9 H12 - ) with N-heterocycles has been developed by using 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) as an oxidant. This metal-free B-N coupling strategy, in both inter- and intramolecular fashions, gave rise to a wide array of charge-compensated, boron-substituted nido-carboranes in high yields (up to 97 %) with excellent functional-group tolerance under mild reaction conditions. The reaction mechanism was investigated by density-functional theory (DFT) calculations. A successive single-electron transfer (SET), B-H hydrogen-atom transfer (HAT), and nucleophilic attack pathway is proposed. This method provides a new approach to nitrogen-containing carboranes with potential applications in medicine and materials.