Metal(salen) Complex Catalysed, Asymmetric Synthesis of (S)-2-hydroxy- (3-Phenoxyphenyl)acetonitrile Derivatives

The synthesis of (S)-2-hydroxy-(3-phenoxyphenyl)acetonitrile derivatives (components of pyrethroid insecticides) by the asymmetric addition of three different cyanide sources to 3-phenoxybenzaldehyde is investigated. Titanium and vanadium(salen) complexes are used as asymmetric catalysts and the processes are analyzed on the basis of both degree of asymmetric induction and relative cost to determine the commercially most viable synthesis. This provides a greener route to pyrethroid insecticides since the enantiomers of synthetic pyrethroids have different insecticidal activity, toxicity and environmental persistence. Thus, by producing only the stereoisomer with the most desirable properties, the production of waste and material with inferior effects on biological organisms and the environment can be avoided.