From: Herb Hedgecock (h.hedgec$##$morehead-st.edu)
Date: Fri Jun 04 1999 - 15:37:12 EDT
On Fri, 4 Jun 1999, Matthew Orr wrote:
> Do you need to proceed through the ethylbenzene? If you're looking to
> make a substituted phenyl acetic acid, you could try starting with a
> substituted styrene derivative. Treat the styrene to
> hydroboration/oxidation conditions, then oxidize the resultant terminal
> alkene with Jones reagent.
One of the problems with hydroboration of styrenes is that they aren't very
regioselective, or at least styrene itself gives a rather large percentage
of the benzylic alcohol. I suppose after the oxidation, separation of the
phenylacetic acid derivative and the acetophenone derivative could be done.
One could improve the selectivity by using some dialkylborane for the
hydroboration, and increase the selectivity quite a bit.
Still another alternative would be to react a alpha-bromotoluene
intermediate with Mg, then carbon dioxide if the ring substituent were
stable to these conditions. It's fairly easy to brominate a methyl on a
benzene ring.
Or have a bromobenzene derivative, react with Mg and then with ethylene
oxide (and later oxidize).
Back to the idea of reacting the ethyl at the primary carbon: I have looked
in a few references and can't find any reaction suggesting this could be
done, but I've not done a very extensive search. It seems that every
reaction I know always favors the benzylic position. Hence, not what you
want.
Herb Hedgecock, PhD |)runrun |)
Dept of Physical Sciences || run ||
Morehead State University || run ||
Morehead KY 40351 ||run run||
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