From: Marko Hapke (marko.hapke$##$mail.uni-oldenburg.de)
Date: Mon Sep 02 2002 - 10:14:49 EDT
>
>
>I wish to Dehydroxylate an organic compound.The
>conventional methods used to do this are rather harsh,
>detrimental to other functional groups in the
>molecule,
>involve expensive reagents and difficult conditions.
>I have theoretically come up with a possible method.
>I want the following : R-OH -> R-H
>This is how I have proposed the method / steps :
>R-OH + HBr(48% sol) -> R-Br + H2O ....1
>
This step should be no problem, if you use alkyl halides.
>R-Br + Zn (powder) -> R-ZnBr ....2
>
This step would be more difficult, but could be accomplished in better
yield if you use Rieke zinc instead of powder. It's much more easy, if
you use LiAlH4. A milder method will be the reduction with NaBH4 in a
dipolar aprotic solvent (DMSO, DMF, sulfolane), that reduces halides
without affecting groups, that would be reduced by LiAlH4 like COOH,
COOR and CN.
>(Note: R contains an ester group)
>Compare to GRIGNARD reaction :
>R-MgI + H2O -> R-H + MgI(OH).
>The above is used to destroy excess Grignard reagent.
>It cannot be used in reactions where there is an ESTER
>group,as the R-MgI will react with it.
>
You can use Grignard reagents, but you have to do it at deep
temperatures and with the trick that you use another Grignard reagent
like iPrMgCl to make the Grignard of your own compound which could be
reduced at deep temperatures with a simple alcohol.
Hope this helps
Marko
_______________________________________
Marko Hapke
Dipl.-Chem.
Carl von Ossietzky University Oldenburg
Department of Chemistry
P. O. Box 2503
D-26111 Oldenburg
Germany
Tel.: 0049 / (0)441 / 798-3726 or -3699
Fax: 0049 / (0)441 / 798-3329
E-mail: marko.hapke$##$mail.uni-oldenburg.de
_______________________________________
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