Axially chiral spiranes are pivotal ring systems widely found in natural products, pharmaceutics, materials, and ligands. However, the asymmetric synthesis of their silaspirane counterparts has rarely been reported. Silaspiranes have attracted particular attention due to their chiral spiro-silicon center, which serves as an ideal carbon isostere and can endow spiro-analogs with distinct properties.

Distinct from previously reported cyclization or cycloaddition strategies to form 5/5-silaspiranes, prof. Zhenlei Song's group report the asymmetric dual ring expansion of spirosilabicyclobutanes with alkynes to synthesize axially chiral spirosilabicyclohexenes bearing a novel 6/6-silaspirane framework. DFT (density functional theory) calculations provide the deep insight into the origin of the high enantioselectivity controlled by the sterically demanding binaphthyl phosphoramidite ligand. Preliminary studies of chiroptical properties indicate that one of the spirosilabicyclohexene analogs exhibit fluorescence emission, Cotton effects and CPL (circularly polarized luminescence) activity. (Angew. Chem. Inter. Ed.(https://doi.org/10.1002/anie.202212889)).