Rosenmund synthesis nitrile

Fig. 16.8. Rosenmund-von-Braun synthesis of aromatic nitriles taking the preparation of pora-acetylbenzonitrile as an example.

The synthesis of aldehydes by the Sommclet reaction, the Rosenmund reduction and the Stephens reaction all involve the conversion of a group already present in the molecule. The Rosenmund reduction (Scheme 6.7) is the catalytic hydrogenation of a benzoyl chloride in the presence of a catalyst poison, quinoline/sulfur, which prevents over-reduction to the alcohol. In the Stephens reaction (Scheme 6.7), a nitrile group is reduced by tin(II) chloride and hydrochloric acid to an imine salt, which is then hydrolysed. 

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. ... 

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

Conventional organic synthesis for aromatic nitriles [e. g. 10], for example the Rosenmund-von Braun reaction, the Sandmeyer reaction, or the oximation of aldehydes in the presence of dehydrating agents, performed in batch processes, are cumbersome and result in different amounts of by- and waste products. The ineffectiveness of such processes with regard to the amount of feedstock necessary per formed nitrile and the waste produced is rather high (in terms of the effectiveness factor defined by Sheldon [11]). 

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

An increasing application of N-methylpyrrolidone as a reaction medium has been noticed, e.g. in the Rosenmund-v. Braun nitrile synthesis , the halogenation of acetylene derivatives , and the synthesis of ethynylcarbinols . Pyridine is an excellent solvent for lithium aluminum hydridef reactions . 

Friedman modification of the Rosenmund-v. Braun nitrile synthesis. A mixture of 2,5-dibromoterephthalic acid, GuGN, and dimethylformamide heated slowly with stirring to reflux, after 1 hr. poured into a soln. of FeGlg in aq. HGl, and warmed 10 min. at 60° to decompose the complex pyromelitimide. Y ... 

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. 

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. 

Koelsch CF, Whitney AG (1941) The Rosenmund-von Braun nitrile synthesis. J Oig Chem 06(6) 795-803... 

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