Rosenmund–von Braun reaction

The Rosenmund - von Braun reaction is a name reaction in organic chemistry and is used for the production of aryl nitriles from aryl halides. In 1919, she was discovered by Karl Wilhelm Rosenmund and modified in 1931 by Julius von Braun.

Overview reaction

The preparation of aryl nitriles (e.g., benzonitrile ) from aryl halides (e.g. phenyl bromide ) runs with the addition of an excess of copper ( I) cyanide in a polar, high boiling solvent (e.g., pyridine, dimethylformamide (DMF), nitrobenzene ) under reflux for:

The Rosenmund - von Braun reaction is a nucleophilic aromatic substitution reaction and is related to the Sandmeyer reaction, which proceeds under radical conditions. Likewise, it has similarities with the Stephens - Castro coupling.

Mechanism

A possible mechanism - explained here using the example of phenyl bromide - can be understood by the formation of a Cu ( III) species. There follows a two-step addition-elimination mechanism as in nucleophilic aromatic substitution often the case. The first step involves the oxidative addition of Phenylbromids ( 1) with the kalatylisch active Cu ( I) species in the copper cyanide. The resulting Cu ( III ) intermediate 2 reacts by reductive elimination to Phenylcyanid (3) and copper bromide.