Design, Synthesis and Application of Chiral Spirocyclic Bisindoles

While modifications of the privileged catalyst backbones, such as 1,1'-spirobiindane-7,7'-diol (SPINOL), have led to the development of diverse useful chiral catalysts, the incorporation of heteroarenes in such chiral spirocyclic structures has limitedly known. Herein we report the design of a type of chiral spirocyclic bisindole skeletons where the electronically distinct heteroarenes serve as direct anchor for functional sites. Separate approaches for the synthesis of two different families of such skeletons have been developed via chiral phosphoric acid and rhodium catalysis, respectively. Both strategies provided expedient access to the highly enantioenriched spiro-bisindoles, owing to not only the high nucleophilicity of the indole ring, but also the robust asymmetric control. These new skeletons have been demonstrated as backbones of effective chiral catalysts for both transition metal catalysis and organocatalysis.