Synthesis and Properties of Sila[n]helicenes via Dehydrogenative Silylation of C–H Bonds under Rhodium Catalysis

Use of a rhodium catalyst with (R)-(S)-BPPFA ligand allows efficient synthesis of sila­[n]­helicenes via dehydrogenative silylation of C–H bonds. By selecting the proper ligands, the current method provides the ability to prepare unsymmetrical sila­[n]­helicene derivatives without any oxidants. The resulting sila­[6]­helicene is a rare example of a five-membered ring-fused [6]­helicene, which was isolated as a single pure enantiomer without substituents on the terminal benzene rings.