Goldberg reaction

Ullmann condensation
Named after	Fritz Ullmann
Reaction type	Coupling reaction
Identifiers
Organic Chemistry Portal	ullmann-reaction
RSC ontology ID	RXNO:0000081

The Ullmann condensation or Ullmann ether synthesis is a variation of the Ullmann reaction, in which a phenol is coupled to an aryl halide to create a diaryl ether in the presence of a copper compound, named after Fritz Ullmann. The corresponding aniline or aryl amide reaction is sometimes called Goldberg reaction, named after Irma Goldberg.

An example is the synthesis of p-nitrophenyl phenyl ether

An active copper powder that is required for this reaction can be prepared by the reduction of copper sulfate by zinc metal in hot water causing the precipitation of elemental copper.

The reaction often requires high-boiling polar solvents such as N-methylpyrrolidone, nitrobenzene or dimethylformamide and high temperatures (often in excess of 210 °C) with stoichiometric amounts of copper. The aryl halide is activated by electron-withdrawing groups or carries a carboxylic acid group in the aromatic ortho position. The research field was revitalized with the introduction of catalytic copper reactions in 2001–2003 using up to 0.1 equivalent copper iodide, base and a diamine ligand.

An example of a Goldberg reaction is the synthesis of fenamic acid, an intermediate of acridone via the Goldberg reaction:

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