Ullmann diarylether synthesis

In addition to copper(I) halides, copper(II) oxide was found to be an effective catalyst in the Ullmann diarylether synthesis [59, 145, 146] and was used for the preparation of several diarylethers in our laboratory [146]. Cu(I) oxide was first applied by Tomita et al. in the reaction of bromobenzene with 4-hydroxyphenyl acetic acid and they obtained the corresponding diarylether in 60% yield [147]. 

With alcohols or more often with alcoholates (refs. 51 - 56) or phenolates (refs. 57 - 64) the arylethers are formed. Typically, one of the Ullmann reactions is corresponding to the diarylethers synthesis. 

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