The Pschorr Reaction allows the preparation of biaryl tricyclics by intramolecular substitution of one arene by an aryl radical. This radical is generated in situ from an aryl diazonium salt by copper catalysis. Although excess copper salts are used, the yield is normally moderate.
Alternative one-electron donors that are more soluble have recently been discovered (see recent literature). The reported method leads to improved yields in a shorter reaction time.
Mechanism of the Pschorr Reaction