Photochemical Functionalization of Helicenes

Abstract

Herein, a visible-light photochemical approach for practical helicene functionalization at very mild reaction conditions is described. The photochemical reactions allow for the regiospecific and innate late-stage functionalization of helicenes and are easily executed either through the activation of C(sp² )-Br bonds in helicenes using K₂ CO₃ as inorganic base or direct C(sp² )-H helicene bond functionalization under oxidative photoredox reaction conditions. Overall, using these transformations six different functional groups are introduced to the helicene scaffold through C-C and four different C-heteroatom bond-forming reactions.

Keywords: C−H activation; electron transfer; helicene functionalizations; organic dyes; photoredox; visible light.