Asymmetric Synthesis of Azahelicenes via CPA-Catalyzed Kinetic Resolution

Abstract

The azahelicenes are structurally fascinating and practically useful chiral scaffolds, but their synthesis, especially in a catalytically asymmetric manner, is rather challenging. Herein, we report a CPA-catalyzed transfer hydrogenation process, which enables a rapid kinetic resolution of aza[6]helicenes. The established strategy provides facile access to enantioenriched aza[6]helicenes and tetrahydro[6]helicenes from easily available starting materials. A gram-scale reaction and facile conversion of the helical products into a promising chiral Lewis base catalyst, a chiroptical switch material, and monophosphine ligands further highlight the potential application of this protocol.