Ullmann condensation

The Ullmann condensation or Ullmann ether synthesis is a variation of the Ullmann reaction, in which a phenol is coupled to an aryl halide to a diaryl ether in the presence of a copper compound.^[1] The corresponding aniline or aryl amide reaction is sometimes called Goldberg reaction, named after Irma Goldberg.^[2]

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An active copper powder that is required for this reaction can be prepared by the reduction of copper sulfate by zinc metal in hot water causing the precipitation of elementary copper.

Recently an Ullmann-type aromatic amination reaction between an aryl iodide and an aryl amine as coupling partners has been published.^[5] The catalyst used is formed from copper(I) iodide and phenanthroline. As this reaction proceeds well with an electron-rich aryl iodide it is a valuable alternative to the Buchwald-Hartwig amination reaction, which gives best yields with electron-poor aryl halides.

References

1. ^ Fritz Ullmann and Sponagel, Chem. Ber, 1905, 38, 2211.
2. ^ I. Goldberg, Chem. Ber. 1906, 39, 1691.
3. ^ Ray Q. Brewster and Theodore Groening, "Ether, p-nitrophenyl phenyl", Organic Syntheses, Coll. Vol. 2, p.445 Online article
4. ^ C. F. H. Allen and G. H. W. McKee, "Acridone", Organic Syntheses, Coll. Vol. 2, p.15. (Online article)
5. ^ H.B. Goodbrand, Nan-Xing Hu, "Ligand-Accelerated Catalysis of the Ullmann Condensation: Application to Hole Conducting Triarylamines", J. Org. Chem 1999, 64, 670-4. DOI