Synthesis of Diaryl Ethers Using an Easy-to-prepare, Air-stable, Soluble Copper(i) Catalyst

We have found that bromo(triphenylphosphine)copper(I), an air-stable and soluble copper(I) complex, can be used as a catalyst in the synthesis of diaryl ethers. Using this catalyst, we have synthesized diaryl ethers from electron-rich aryl bromides and electron-rich phenols in the presence of cesium carbonate, in 17–24 h, in NMP. We also found that electron-deficient aryl bromides couple with phenols in the presence of cesium carbonate, in 6 h in NMP at 70 C, without the catalyst. The classical copper-mediated Ullmann coupling is the reaction of choice for the synthesis of aryl ethers and triarylamines in large and industrial scales. These reactions often require high temperatures ( 200 C) and the use of copper salts in greater than stoichiometric amounts. The reaction