Modern Photo- and Electrochemical Approaches to Aryl Radical Generation

Polish National Science Centre, Sonata 2021/43/D/ST4/02267); Polish National Science Centre, Sonata (UMO-2020/39/D/ST4/01510); scholarship awarded by the Polish Ministry of Education and Science to outstanding young scientists (B.Sadowski).

Aryl rings appear in a plethora of natural products or drugs. A vast majority of arylation processes still rely on the utilization of transition-metal complexes as catalysts. Another important strategy for introducing aryl rings into an organic skeleton operate through a radical pathway. The chemistry of aryl radicals has witnessed rapid development during the last century, especially as these species are crucial intermediates in many synthetically-meaningful organic transformations, such as the Sandmeyer or Pschorr reactions. Predominately, they are prepared employing conventional redox reagents (oxidants or reductans) that are often used in large excess. In turn, recent developments in photocatalysis and synthetic electrochemistry allow for the assembly of Ar• species in a more sustainable and straightforward way, however, these advancements have not been timely and critically summarised so far. This Review fills this obvious gap and sum up recent advances in processes involving Ar• by highlighting some challenges and identifying potential areas of improvement, which might inspire future research endeavors in this topic.