Phenylvaleric Acid and Cognate Acids

Synthesis of this acid is less demanding (Reaction scheme 187), and therefore only a few alternatives appeared in the patent hterature. 

This principle was applied to similar variations [520]. Production of pure benzyl chlorides sometimes poses a technical problem, giving a reason for better proposals [521]. 

More exotic methods are chemically interesting, for example the oxidative rearrangement of phenylalkylketones 264 (Reaction scheme 188) with thalliumnitrate in orthoester as the solvent [522]. 

Arylalkyl ketones rearrange on treatment with phosphoryl azides to give the phosphorylated amide of fenvaleric acid (Reaction scheme 191) [526]. 

A close analogue is the acid 267 for flucythrinate. Some methods of preparing the 4-difluoromethoxyphenyl isovaleric 267 acid are described in Reaction scheme 192  

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