Synthesis of Symmetrical Diaryl Ketones by Cobalt-Catalyzed Reaction of Arylzinc Reagents with Ethyl Chloroformate

Symmetrical diaryl ketones were prepared by a cross-coupling reaction between aryl bromides and ethyl chloroformate. This new method, which uses a catalyst composed of CoBr2 and a bipyridine ligand along with readily available starting materials, allows for the synthesis of a variety of symmetrical diaryl ketones in moderate to excellent yields (37-99%) under mild conditions. This reaction, in which ethyl chloroformate acts as a surrogate of carbon monoxide in the presence of cobalt and zinc, represents an interesting alternative to previously known approaches for the synthesis of diarylmethanones.