Rhodium-Catalyzed Synthesis of Chiral Spiro-9-silabifluorenes by Dehydrogenative Silylation: Mechanistic Insights into the Construction of Tetraorganosilicon Stereocenters
constitutional isomers. The reaction proceeded through two consecutive dehydrogenative silylations, and the absoluteconfiguration was determined in the first silylative cyclization. Competitive reactions with electron‐rich and electron‐deficient dihydrosilanes indicated that the rate of silylative cyclization increased with decreasing electron density on the silicon atom of the starting dihydrosilane. Further
Si goes chiral: Treatment of a bis(biphenyl)silane with a catalytic amount of a rhodium complex gave a spirosilabifluorene bearing a quaternary silicon atom. By using a rhodiumcatalyst with a chiralphosphine ligand (see scheme), asymmetric dehydrogenative cyclization proceeded to give chiralderivatives in good yields and enantioselectivities.