Metal- and ligand-free Ullmann-type C-O and C-N coupling reactions promoted by potassium tert-butoxide

A simple, metal- and ligand-free procedure for the Ullmann-type C-O coupling reactions has been achieved by allowing aryl bromides to react with a variety of phenols in the presence of t-BuOK. Moderate to excellent yields of O-arylation products are obtained under mild conditions in a short time. In addition, two examples of C-N coupling reactions are also reported. A benzyne mechanism is proposed according to the experiment data.