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.
Further display options for biaryls:
^ 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.