ORGLIST: Re: Everybody Digest, Vol 10, Issue 15

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From: Lakshmipathi (plpathi$##$hotmail.com)
Date: Sun Jul 31 2005 - 16:13:36 EDT


1. borohydride reduction reaction workup (diogo$##$unilavras.edu.br)
Hi
you must try quenching the reaction by adding aqueous NaOH and isolate the
product. If you have problems still, you might want to isolate the amine as
carbamate (Boc) and after getting the pure carbamate, try cleaving the
carbamate to get the pure amine...
all the best
Pathi

email; pathi$##$neu.edu
          plpathi$##$hotmail.com

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Sent: Sunday, July 31, 2005 12:05 PM
Subject: Everybody Digest, Vol 10, Issue 15


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> 1. borohydride reduction reaction workup (diogo$##$unilavras.edu.br)
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> Message: 1
> Date: Sat, 30 Jul 2005 17:57:37 -0300 (BRT)
> From: diogo$##$unilavras.edu.br
> Subject: ORGLIST: borohydride reduction reaction workup
> To: everybody$##$orglist.net
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> <65169.200.159.217.8.1122757057.squirrel$##$webmail.unilavras.edu.br>
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> Hello you all!
> I'm working on some glicoside-derived amines and I had problems concerning
> to the final step: amination. I tried reductive amination with some
> glicosides thru their formyl groups and using sodium cianoborohydride. As
> the reactions didnīt shwo favorable I turned the metodology to the
> sequence in which I first prepare an imine derivative and then it is
> reduced to the correspondent amine compound. This reduction reaction
> workup has been the problem: Iīm using sodium borohydride since itīs a
> mild reagente (the glicoside linkage wouldnīt resist some other
> reagents...)and catalytic hydrogenation led to hydrogenolysis of the
> product. I am sucessfull with the reduction (TLC, NMR, IV) but the product
> is as water soluble as the byproducts of reduction. Iīve been preparing
> the imine in metanol and using the same solvent in reduction. although
> itīs quite a small quantity of the impurity I need the compouns very pure
> since they will be submitted to biological testes. How can I solve this,
> please? I tried columm cromat. but only metanol elutes the product (and
> "all" the silicagel)and I donīt have acess to many others stacionary
> phases...
> Iīll be thankfull with any help.
> Diogo
>
>
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