Aryl halides with a benzene ring directly bonded to a halogen atom are readily available and chemically stable, so they are used as a source of benzene rings in organic synthesis. For example, a chemical reaction that generates a highly reactive aryl radical from an aryl halide using a toxic tin compound has long been known as a method for supplying a benzene ring. In recent years, chemical reactions have been developed in which an aryl halide is reduced using a metal catalyst or a photocatalyst followed by cleavage of the bond between the benzene ring and the halogen atom to generate an aryl radical. However, since the methods previously reported require metal salts and/or excess amounts of an oxidizing agent or a reducing agent, chemical reactions with less environmental impact are desirable.
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Source: Phys.org