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 200°C) 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.