Ullmann aryl-aryl coupling

What is Ullmann aryl-aryl coupling?

The Ullmann aryl-aryl coupling, also known as the Ullmann reaction, refers to the copper-mediated coupling of aryl halides. Additionally, the reaction can be used to synthesize biaryl ethers from aryl halides and phenols.

Ullmann aryl-aryl coupling - Ullmann reaction
Ullmann aryl-aryl coupling

It was developed by Fritz Ullmann in the early 20th century and has since become a widely used method in organic synthesis..

The reaction involves the use of a copper-based catalyst, such as copper(I) iodide CuI or copper(II) acetate Cu(OAc)2, and a coupling partner, such as an aryl halide or an aryl sulfonate. The aryl groups are treated with these reagents, resulting in the formation of a new aromatic compound..

One of the main advantages of the Ullmann aryl-aryl coupling is that it allows for the synthesis of a wide range of aromatic compounds, including those containing complex functional groups. It is also a useful method for synthesizing compounds with high molecular weights and for introducing aryl groups onto complex scaffolds..

However, there are also some limitations to the Ullmann aryl-aryl coupling. It requires the use of toxic and expensive reagents, such as CuI, and can be sensitive to the conditions of the reaction. In addition, the reaction may not always be efficient, and may produce low yields in some cases..

Despite these limitations, the Ullmann aryl-aryl coupling remains a valuable tool in the synthesis of aromatic compounds, and has been used in the synthesis of a variety of chemicals, including pharmaceuticals, fragrances, and dyes..