Thank you for all contributions to the problem: oxidation of substituted
ethylbenzene to substituted phenylacetic acid.
Allmost all contributions say, that the direct oxidation of ethylbenzene
to phenylacetic acid is not possible, since benzoic acid is formed.
One possible way is the oxidation of (substituted) acetophenone using
elementar sulphur and morpholine. This reaction is called
Willgerodt-Kindler-reaction. Unfortunately H2S is formed after
hydrolysis, which can be a great disadvantage of this reaction.
Another proposal was to start with a substituted styrene derivative,
which can be oxidized by hydroboration. However, hydroborations are not
very regioselective, or styrene itself gives a rather large percentage
of benzylic alcohol. Selectivity can be increased by using some
dialkylborane.
Another possibility is the Grignard reaction of alpha-bromotoluene using
Mg and carbon dioxide or of bromobenzene using Mg and ethylene oxide
with following oxidation.
An usual way is the chloromethylation of benzene to obtain
benzylchloride, followed by cyanuration to get the benzylnitrile, which
can  be hydrolysed to the desired acid.
Now, I will think, which way I will try at first. Another possibility
could be also the Reformatsky reaction from substituted phenylbromide
and alpha-bromo ethyl acetate with activated zinc and Ni(PPh3)4
catalyst.

Cornelia
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