Ring Expansion of Benzofurans by Single-Silicon Insertion.

Given the importance of organosilicon compounds in medicinal chemistry, the insertion of a silicon atom into a readily available heterocycle is a powerful yet underdeveloped scaffold-hopping strategy for expanding drug-like chemical spaces. Herein, we report a Ni-catalyzed single-silicon atom insertion reaction for the transformation of readily available benzofurans into their corresponding high-value oxasilacycles. The reaction involves the C-H bond silylation of benzofurans and 1,2-oxygen migration. The resulting oxasilacycles serve as versatile synthons for generating various compounds and provide access to different cyclic skeletons such as oxaborins, coumarins, benzooxepines, and polycyclic oxasilaalkanes, thereby diversifying the initial benzofuran core. This study establishes a versatile platform for the skeletal editing of benzofurans, broadening the synthetic toolbox for medicinal chemistry.