Re: ORGLIST: Everybody Digest, Vol 36, Issue 3

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From: Gaurav Sharma (gaurav0sharma$##$gmail.com)
Date: Wed Jul 04 2007 - 12:36:32 EDT


Regarding Isocyanates.... (Ohad Ilovich)
It is quite difficult to purify isocyanates as they are very reactive and so
they are prepared in situ and used for next step. I think here you can treat
one of the amine with 4-nitrophenyl chloroformate to make a carbamate and
then treat with another amine under cat. amount of DMAP in dioxane under
refluxing conditions for 4-5 h.I think it will work out!!!
regards
Gaurav Sharma..

On 7/4/07, everybody-request$##$orglist.net <everybody-request$##$orglist.net>
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> 1. Isocyanates.... (Ohad Ilovich)
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> Message: 1
> Date: Tue, 3 Jul 2007 18:33:32 +0300
> From: "Ohad Ilovich" <ilovich$##$pob.huji.ac.il>
> Subject: ORGLIST: Isocyanates....
> To: <everybody$##$orglist.net>
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> Dear all,
> I have asked about creating an urea here before and recieved some help in
> the matter and decided to try my luck once again. I have two questions:
> 1) I have an aniline which i react with triphosgene to form an isocyanate.
> this isocyanate is then reacted with another aniline (picomolar amounts of a
> radioactive aniline) to form an urea bond. I cannot seem to get a good
> isocyanate. sometimes when i add the second aniline i get a complete
> reaction in 30 mins at room temp. and sometimes no reaction at all.
> Is there a way to isolate the isocyanate? Is there a way such as IR to
> make sure it is pure isocyanate? Can i do column chromatography in a glove
> box?
> we can buy high-purity isocyanates so there must be a way to do this....
> 2) can anyone give me any further ideas about precursors for urea bond
> formation?
> I have tried isopropenyl as a leaving group without much success and I
> know CDI is used (but mostly aliphatic amines)
> any ideas and referance aritcles will be most welcome
>
> Ohad Ilovich
>
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-- 
Freedom is not worth having if it does not include the freedom to make
mistakes.
Mahatma Gandhi
(1869 - 1948)

Gaurav Sharma

M.S.(Pharm) Dept. of Medicinal Chemistry. NATIONAL INSTITUTE OF PHARMACEUTICAL EDUCATION AND RESEARCH (NIPER) Sector- 67, Phase- X, S.A.S. Nagar, Mohali, Punjab-160 062 INDIA.

Email: gaurav0sharma$##$gmail.com Phone: +91-9888-28-48-08

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