From: Frederic Denonne (frederic.denonne$##$iecb-polytechnique.u-bordeaux.fr)
Date: Wed Sep 15 1999 - 02:41:32 EDT
At 22:42 14/09/99 -0700, you wrote:
>
>Hello
>I am Priya Joshi, a Ph.D student. I am having difficulty in bromination of
>Methyl-2,4-dimethoxyphenylacetate. I want the bromination at the alpha
>position (i.e. at benzylic position).But when I tried NBS, bromination
>occurred at the Benzene ring.
>
>Does anybody know How to bring about benzylic bromination without ring
>bromination.
You should arrange to obtain radicals in your reaction medium. To do this, you
could try irradiating your solution with sun light (to break the N-Br bond
homolytically). The aromatic substitution (that you obtain) comes when you
break that same N-Br bond heterolytically, liberating Br+ ions.
Hope this helps,
--------------------------
Frederic Denonne: <http://poujeaux.iecb-polytechnique.u-bordeaux.fr/>
IECB - Ecole Polytechnique
ENSCPB - Av. Pey Berland BP108
33402 Talence Cedex
France
+ 33 5 57 96 22 29 (CET) / Fax: ... 22 26
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