Rhodium-Catalyzed Asymmetric Synthesis of Silicon-Stereogenic Dibenzosiloles by Enantioselective [2+2+2] Cycloaddition

A rhodium-catalyzed asymmetric synthesis of silicon-stereogenic dibenzosiloles has been developed through a [2+2+2] cycloaddition of silicon-containing prochiral triynes with internal alkynes. High yields and enantioselectivities have been achieved by employing an axially chiral monophosphine ligand, and the present catalysis is also applicable to the asymmetric synthesis of a germanium-stereogenic dibenzogermole. Preliminary studies on the optical properties of these compounds are also described.