Borenium-ion-catalyzed hydrogenation of arenes

Non-metal-catalyzed hydrogenation of arenes represents a sustainable and environment-friendly approach for the synthesis of cyclohexane derivatives. Herein, we report the development of a borenium-ion catalyst system which can hydrogenate a number of monocyclic arenes. Additionally, this metal-free catalytic system allows selective partial or full hydrogenation of naphthalene and anthracene by modification of the reaction conditions. Our mechanism studies suggest that the borenium-arene-mediated H 2 splitting takes place before the rate-limiting step and the hydride transfer between the resulting neutral borane and protonated arene is likely the rate-limiting step in the catalytic process. Metal-free hydrogenation of arenes was achieved by using a borenium ion as the catalyst.