Rosenmund synthesis, aldehyde nitrile

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. 

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]). 

---