Sila-spirocyclization involving unstrained C(sp 3 )-Si bond cleavage.

C - Si Bond cleavage is one of the key elemental steps for a wide variety of silicon-based transformations. However, the cleavage of unstrained Si-C(sp 3 ) bonds catalyzed by transition metal are still in their infancy. They generally involve the insertion of a M - C(sp 2 ) species into the C - Si bond and consequent intramolecular C(sp 2 )‒Si coupling to exclusively produce siloles. Here we report the Pd-catalyzed sila-spirocyclization, in which the Si-C(sp 3 ) bond is activated by the insertion of a M - C(sp 3 ) species and followed by the formation of a new C(sp 3 )‒Si bond, allowing the construction of diverse spirosilacycles. This reactivity mode, which is strongly supported by DFT calculations may open an avenue for the Si-C(sp 3 ) bond cleavage and silacycle synthesis.