Rhodium-Catalyzed 2-Arylphenol-Derived Six-Membered Silacyclization: Straightforward Access toward Dibenzooxasilines and Silicon-Containing Planar Chiral Metallocenes

摘要

The C/Si switch strategy has been regarded as a useful and efficient strategy for the discovery of drugs and materials. Thus, development of a methodology to access diverse silacycles is of great significance and in great demand. Among these, C-H bond silylation provides a powerful and straightforward synthetic method to form diverse silacycles in an atom- and step-economical fashion. However, C-H bond silylation has not been used to access any six-membered silicon-bridged pi-conjugated scaffolds and enantioselective six-membered C-H silylation has never been presented. Herein, we successfully accessed diverse six-membered pi-conjugated dibenzooxasilines via C-H bond silylation and investigated their photophysical properties. Furthermore, we realized enantioselective six-membered C-H siylation to directly afford planar chiral metallocene oxasilolanes with high ee (up to 95% ee). We also demonstrated the synthetic usefulness of dibenzooxasilines and planar chiral metallocene-fused benzooxasilolines as valuable synthetic intermediates via diverse additional transformations. Moreover, six-membered silicon-bridged ladder pi-conjugated systems were designed and rapidly constructed by using our methods. The "isomerization" and "silicon" effects on molecular geometries and photophysical properties were also evaluated in detail.