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Ullmann Reaction

Ullmann reaction   Named Reactions in Organic Synthesis
Reaction category:
Transition metal-catalyzed couplings

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During 1901F.Ullmann discovered that by reacting two equivalents of an aryl halide with one equivalent of copper powder at high temperature a symmetrical biaryl compound was formed. The condensation of two aryl halides in the presence of copper to create biaryl products is now known as the Ullmann reaction. Since then many differing symmetrical and unsymmetrical biaryl have been synthesized using this route. Reaction efficiency can be improved by activating the copper prior to use. This can be achieved by reducing copper iodide with lithium naphthalenide or reducing copper sulphate with zinc powder. Usually temperatures greater than one hundred degrees are required to initiate the coupling but using activated copper allows lower temperatures to be used. The most common solvent used is Dimethyl formamide (DMF) but for higher temperatures nitrobenzene or para nitro toluene can be used.

The first total synthesis of the natural product Taspine , an alkaloid which acts as a potent acetylcholinesterase inhibitor, by T.R. Kelly and co-workers utilized the Ullmann reaction to create the central biaryl link.

Mechanism of the Ullmann Reaction

mechanism of Ullmann reaction



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Pericyclic and photochemical reactions NEW!

Radical reactions

Electrophilic aromatic substitution

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Heterocycle formation

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Some relevant Alfa Aesar products for the Ullmann reaction:
Copper, powder, 99+%
Copper(I) iodide, 98%
Copper(I) iodide, Puratronic®, 99.998% (metals basis)
Copper(II) sulfate, anhydrous, Reagent Grade
Zinc powder, -100 mesh, 97+%

We have many aryl halide building blocks.

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