Re: ORGLIST: deprotection of carbamate

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From: Uno Mäeorg (uno$##$chem.ut.ee)
Date: Wed Apr 21 1999 - 04:19:58 EDT


Dear Prof. DUFRASNE FRANCOIS

At first, I think you are talking about ethoxycarbonyl group. There are
many of possibilities for selective and mild cleavage of carbethoxy or
other alkoxycarbonyl groups, like Boc, Z, Troc etc. Best review is In J.
Kocienski Protecting Groups,Thieme N-Y 1994. And new data in Chemical
Communication in one of issuses January or February.
About several methods of removing Boc group you can read Liebigs Ann.
Chemie 749, 90-108 (1971).
If you have imidodicarbonate structure you can effectively use magnesium
perchlorate in acetonitrile as described in Tetrahedron Letters 1993, 34,
7873-7876 or new modification of this Tetrahedron Letters 1998, 39,
681-684. The last one is the best to exchange the old method 1.5 eq of TFA
in methylene chloride (for Boc) what is slow and not very selective in case
of sensitive groups.
If you don't wont to use TFA (sometimes TFA amine salts are liquid), you
can use 4M HCl/dioxane, what is also working perfectly -fast and clean
reaction.


Good luck

Uno Maeorg
Associate Professor
Institute of Organic Chemistry
University of tartu
  


At 07:09 PM 4/20/99 +0200, DUFRASNE FRANCOIS wrote:
>Hello to everybody,
>
>I've synthetised a primary amine protected by a carbethoxy group. I want=
 now
>to hydrolyse it under the mildest conditions as possible. A colleague gave
>me the advise to use the trifluoroacetic acid method, in dichloromethane.
>Does anyone know a reference about it?
>
>
>Thanks in advance.
>
>
>
>DUFRASNE FRANCOIS
>Assistant professor
>Laboratoire de Chimie Pharmaceutique Organique
>Université Libre de Bruxelles, Institut de Pharmacie
>Boulevard du triomphe, Campus Plaine, CP 205/5
>1050 Brussels Belgium
>Tél. 00+2+650.52.35 Fax 00+2+650.52.49
>
>__________________
>
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>List coordinator: Joao Aires de Sousa (jas$##$mail.fct.unl.pt)
>
>

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