Ullmann diaryl ether synthesis

What is Ullmann diaryl ether synthesis?

The Ullmann diaryl ether synthesis is a reaction discovered by Ullmann (University of Geneva) in 1904. It involves the coupling of alkali phenoxides and aryl halides in the presence of a copper reagent to form diaryl ethers.

This reaction is also known as the Ullmann reaction, Ullmann coupling, Ullmann ether synthesis, or Ullmann ether reaction, among other names.

Ullmann diaryl ether synthesis - general reaction scheme - Ullmann reaction - Ullmann coupling - Ullmann ether synthesis - Ullmann ether reaction
Ullmann diaryl ether synthesis

Ullmann diaryl ether synthesis is typically carried out at temperatures ranging from 100 to 220 ºC in the absence or presence of an inert solvent. The reactivity of the aryl halides decreases in the order of:

I > Br > Cl >> F

and highly substituted phenols may react with different aryl halides. However, Ullmann diaryl ether synthesis has some drawbacks, such as the need for high temperature and long reaction times, moderate yields, stoichiometric or excess amounts of copper reagent, and dehalogenation.

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