Palladium-catalyzed double activation of Si-C(sp3) bond of benzosilacyclobutenes synergized with unexpected olefin migration and ring-opening hydrolysis

A regioselective silicon-carbon bond activation of silacycles has emerged as a powerful strategy to access organosilicon compounds with functional groups. In contrast, progress in the development of new reaction systems for the tandem and double Si-C bond activation of silacycles has lagged. In this regard, there have been no reports of Si-C(sp³) bond activation of benzosilacyclobutenes and its tandem transformations. Herein, we address this challenging, disclosing the first example of palladium-catalyzed double Si-C bond activation of benzosilacyclobutenes and its tandem ring expansion and ring-opening transformations, in which various functionalized silanols that have ester groups are synthesized in this reaction. The main feature of this novel transformation is the highly selective activation of the Si-C(sp³) bond of benzosilacyles to achieve [4 + 2] cycloaddition with ester-activated alkynes and subsequent ring-opening and σ-bond metathesis with H₂O. Moreover, the DFT studies realized the origin of Si-C(sp³) bond activation, olefin migration, and ring-opening hydrolysis in the unprecedent reaction process.