Rosenmund-von Braun synthesis of aryl

Example 1, A variant, also known as the Rosenmund-von Braun synthesis of aryl nitriles ... 

The Rosenmund-von Braun synthesis of aryl nitriles (40) from aryl halides (38) also shares some commonality with the Castro-Stephens reaction. This transformation was discovered nearly a century ago, and was mentioned in the initial Castro-Stephens publication where the authors noted potential mechanistic similarity. 

For more than a century, stoichiometric methods were presumed in the preparation of benzonitriles in laboratory and industry. These particularly include the Rosenmund-von Braun reaction of aryl halides, the diazotization of anilines and subsequent Sandmeyer reaction, and the ammoxidation. Because of (over)stoichiometric amounts of metal waste, lack of functional group tolerance, and harsh reaction conditions, these methods do not meet the criteria of modern sustainable synthesis. 

Rosenmund—von Braun synthesis. Formation of aromatic nitriles from aryl halides and cuprous cyanide. 

The replacement of an aryl halogen atom by the cyano group can be accomplished by the action of anhydrous cuprous cyanide at 150-250° with or without an organic base (usually pyridine) as a promoter or solvent (Rosenmund-von Braun nitrile synthesis). The reaction is autocatalytic and may be accelerated by the addition of small amounts of a nitrile and Copper sulfate. Typical laboratory procedures are found in the syntheses of a-naphthonitrile (90%) and 9-cyanophenanthrene (87%). The adaptation of the process to commercial practice has been discussed. ... 

The Castro-Stephens reaction is the cross coupling of a copper acetylide (1) and an aryl or vinyl halide (2) to give a disubstituted alkyne (3). The reaction, which shares some common elements with the Sonogashira, Cadiot-Chodkiewicz, Rosenmund-von Braun, Hay, and Glaser coupling reactions, was discovered by Stephens and Castro in the early 1960s and has found some applications in synthesis. " ... 

The typical Rosenmund-von Braun conditions are very harsh (200 °C neat), and product purification is generally troublesome, but the reaction is of historical interest and is occasionally used in the synthesis of simple aryl nitriles. 

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