A Tribute to Ullmann’s Work: Expanding Copper Coil Reactor Applications toward the Hydroxylation of Aryl Bromides

Abstract

Copper coil flow reactors represent an economic, abundant, and durable platform for conducting copper-catalyzed reactions. These have been used in the past for Ullmann-type reactions starting from aryl iodides. However, no procedures have been described for the activation of less reactive aryl bromides. In this work, we successfully developed a method for the hydroxylation of aryl bromides promoted by a copper coil reactor. Notably, the presence of both a diamine ligand and DMF is key for the reaction to proceed. An inorganic base such as Na2CO3 also improved the reaction yield by minimizing the formation of side products. The setup has been applied to a range of disubstituted aryl bromides in moderate to good yields and was tested under 24 h of continuous operation, showing stable yields, thus proving the robustness of the catalysis. Finally, the lifetime of a copper reactor operating under the described conditions has been calculated for the first time, proving that this technology is safe to operate at an industrial scale.