Ullmann reaction

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The Ullmann reaction or Ullmann coupling is the coupling of an aromatic halide with a nucleophile or an aromatic halide with the help of copper powder . It is named after Fritz Ullmann (1875–1939).

Overview reaction

In the Ullmann reaction, two aryl halides - in the example two molecules of chlorobenzene - are linked together:

Overview reaction of the Ullmann reaction

The coupling creates biphenyl .

In general, aryl halides (Ar – Hal) are coupled to form symmetrical biaryls (Ar – Ar). Starting from a mixture of two different aryl halides (Ar 1 –Hal and Ar 2 –Hal), unsymmetrical biaryls of the Ar 1 –Ar 2 type can also be formed in a crossed Ullmann reaction .


The preparation of biaryls ( e.g. biphenyl ) from aromatic halides with the help of copper powder takes place at approx. 200 ° C.

Mechanism of the Ullmann reaction

Further display options for biaryls:

Ullmann coupling

Individual evidence

  1. ^ Z. Wang: Comprehensive Organic Name Reactions and Reagents, 3 Volume Set . John Wiley & Sons, Hoboken, New Jersey 2009, ISBN 978-0-471-70450-8 , p. 2843.