Leaving Groups in Metal-Free Arylations: Make Your Choice!

Cleavage of an Aryl-Leaving Group bond (Ar-LG) is the key step in most arylation processes for the synthesis of highly functionalized (hetero)arenes. In metal-free arylations, depending on the nature of the starting substrates, different thermal and photochemical approaches can be adopted: Single Electron Transfer (SET) and homolysis/heterolysis of an Ar-LG bond to afford an aryl radical (Ar-center dot) or an aryl cation (Ar+), respectively. Accordingly, the nature of LG plays a key-role in determining the mechanism and efficiency of the process.