Copper promoted synthesis of diaryl ethers

An efficient protocol using copper based reagents for the coupling of aryl halides with phenols to generate diaryl ethers is described. A copper(I) complex, [Cu(CH3CN)4]ClO4, or the readily available copper(II) source, CuCO3·Cu(OH)2·H2O (in combination with potassium phosphate), can be used. Aryl halides and phenols with different steric and electronic demands have been used to assess the efficiency of the procedure. The latter source of copper gives better yields under all conditions.