Synthesis of Sulfur- and Oxygen-Bridged Cationic [4]-Helicenes Mediated by Friedel–Crafts-SNAr Tandem Reactions for Red-light-driven Organophotoredox Catalysis

Abstract

The synthesis of sulfur- and oxygen-bridged cationic [4]-helicenes via a tandem Friedel–Crafts–SNAr reaction of a diaryl sulfide or a diaryl ether with a (thio)salicylic acid has been developed. The sulfur-bridged cationic [4]-helicenes are suitable as catalysts for photoredox reactions under low-energy light sources such as red LED light.