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Further Information

Related Reactions
Kolbe Nitrile Synthesis
Ullmann-Type Reaction
Sandmeyer Reaction
Synthesis of Nitriles

Rosenmund-von Braun Reaction

Aryl nitriles can be prepared by the cyanation of aryl halides with an excess of copper(I) cyanide in a polar high-boiling solvent such as DMF, nitrobenzene, or pyridine at reflux temperature.

Mechanism of the Rosenmund-von Braun Reaction

The mechanism probably involves the formation of a Cu(III) species through oxidative addition of the aryl halide. Subsequent reductive elimination then leads to the product:

The excess of copper cyanide and the use of a polar, high-boiling point solvent makes the purification of the products difficult. In addition, elevated temperatures (up to 200C) lower the functional group tolerance. The use of alkali metal cyanides or cyanation reagents such as cyanohydrins, a catalytic amount of copper(I) iodide and kalium iodide, allows a mild, catalytic cyanation of various aryl bromides.

If aryl iodides, sodium cyanide and copper(I) iodide are used, a simple mechanism similar to that of an Ullmann-type reaction can be proposed:

Reactions with aryl bromides and added alkali metal iodides involve additional equilibria in which aryl bromides give the more reactive aryl iodides:

For example, the formation of a copper(III) species and the use of cyanohydrins is discussed by H.-J. Christeau (Chem. Eur. J., 2005, 11, 2483. DOI).

Recent Literature

Copper-Catalyzed Domino Halide Exchange-Cyanation of Aryl Bromides
J. Zanon, A. Klapars, S. L. Buchwald, J. Am. Chem. Soc., 2003, 125, 2890-2891.