Immobilizing Stereogenic Nitrogen Center in Doubly Fused Triarylamines through Palladium-Catalyzed Asymmetric C–H Activation/Seven-Membered-Ring Formation

A series of doubly fused triarylamines containing conformationally stable stereogenic nitrogen centers has been constructed through palladium-catalyzed enantioselective C–H activation and imidoylative cyclization. The cyclization strategy of forming an uncommon seven-membered heterocyclic ring employs readily available functionalized isocyanides and aryl iodides as coupling partners under mild conditions. These helically twisted N-chiral frameworks contain no inner helical substituents or other chiral factors that stabilize the pyramidal conformation at nitrogen.