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.