Activation of C–C Bonds via σ‑Bond Metathesis: Hydroborenium-Catalyzed Hydrogenolysis of Cyclopropanes

High-valent transition metal or main group complex mediated σ-bond metathesis plays an important role in the activation of covalent H–E bonds. However, its involvement in the activation of C–C bonds has remained elusive. Here we describe direct hydroboration of the C–C bonds of cyclopropanes by a hydroborenium complex. Our mechanism study suggests this reaction operates through a σ-bond metathesis pathway. With this hydroborenium complex as a catalyst, hydrogenolysis of unfunctionalized cyclopropanes was achieved, which is unprecedented for homogeneous catalysts and provides an unconventional approach for C–C bond functionalization in the absence of metals.