Asymmetric Brønsted Acid Catalyzed Synthesis of Triarylmethanes - Construction of Communesin and Spiroindoline Scaffolds

Aza-ortho-quinone methides allow the straightforward asymmetric synthesis of natural-product-inspired indole scaffolds possessing a quaternary stereocenter. Our approach provides access to diverse communesin and spiroindoline derivatives with high enantioselectivity under mild reaction conditions. Predictable substitution patterns are found to be the key to our regiodivergent protocols. Two protocols have been developed for the regiodivergent, asymmetric Brønsted acid catalyzed addition of indoles to in situ generated aza-ortho-quinone methides. Furthermore, a new addition spirocyclization sequence leads, depending on the indole derivative, to communesin and spiroindoline cores with quaternary stereocenters.