Ullmannreaktio

The Ullmann reaction is a copper-catalyzed coupling reaction between aryl halides. It is used to form a new carbon-carbon bond, typically between two aryl rings, resulting in biaryl compounds. The reaction requires high temperatures and is often carried out in the presence of a base. Historically, the reaction was often sluggish and required harsh conditions. Early versions of the Ullmann reaction often used copper powder or copper(I) salts as the catalyst. The mechanism involves the formation of arylcopper intermediates, which then undergo oxidative coupling.

Variations of the Ullmann reaction exist, including the Ullmann condensation, which couples aryl halides with phenols or alcohols to form diaryl ethers. Another variation involves the coupling of aryl halides with amines to form diaryl amines. Modern modifications of the Ullmann reaction have led to milder conditions and improved yields through the use of more effective copper ligands and promoters. These developments have expanded the scope and utility of the Ullmann reaction in organic synthesis, particularly for the preparation of complex biaryl systems found in pharmaceuticals and materials science.