ORGLIST: Re: Everybody Digest, Vol 3, Issue 9

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From: Lakshmipathi (plpathi$##$hotmail.com)
Date: Thu Dec 16 2004 - 13:25:04 EST


2. nucleophilic substitution (stephanie)
Hi stephanie
you may try CsF as base in acetontirile as solvent. Actually the anmine as
neat solvent will work if you can afford the amine in excess. Did you try
mitsunobu reaction for this wihtout forming the sulphate of the alcohol...

3. ketal synthesis (Jos? Barros)
Barros
Tartaric acid ester workd fine for the purpose rather than free acid. In one
of the case I have tried the acetonide protection of a diol by using the
acetone/DMSO/trimethyl orthoformate with cattalytic pTSA. You may try this..

4. Deprotection of a trityl group (Ken Knott)
Ken
Trityl ether can be cleaved by acid mediated method, but in the case of
trityl amine, the amine forms a salt and the cleavage may not work well.
Hydrogenolysis should work well, but here again the catalyst get poisoned by
the realeased amine (thats why you see the reaction stops after a while).
You may try Raney Ni and in any case take good amount of catalyst. Sometimes
bubbling H2 helps rather than the simple atmosphere of H2...

Email; plpathi$##$hotmail.com
         lakshmipathi.p$##$astrazeneca.com

----- Original Message -----
From: <everybody-request$##$orglist.net>
To: <everybody$##$orglist.net>
Sent: Thursday, December 16, 2004 10:32 PM
Subject: Everybody Digest, Vol 3, Issue 9

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> Today's Topics:
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> 1. RE: Suggestions (drhodes$##$globalnet.co.uk)
> 2. nucleophilic substitution (stephanie)
> 3. ketal synthesis (Jos? Barros)
> 4. Deprotection of a trityl group (Ken Knott)
> 5. Methyl Lithium-Lithium Bromide complex (Maringanti Krishna)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 15 Dec 2004 13:27:52 +0000
> From: <drhodes$##$globalnet.co.uk>
> Subject: RE: ORGLIST: Suggestions
> To: <everybody$##$orglist.net>, Clyde Davies <deadlyvices$##$hotmail.com>
> Message-ID: <E1CeZC4-0009Q5-St$##$webm9.global.net.uk>
> Content-Type: text/plain
>
> Brilliant idea ... seconded.
>
> Consider hosting a wiki.
>
> Darren.
>
> On Tue, 14 Dec 2004 18:02 , Clyde Davies <deadlyvices$##$hotmail.com> sent:
>
> >Speaking from bitter experience, how about compiling some modern,
reliable
> >replacements for common synthetic transformations? For instance, using
> >TFAA/pyridine instead of POCL3 for dehydration of amides? A sort of
'don't
> >do it like that, do this instead' list?
> >
> >Clyde Davies
> >(ex physical organic chemist)
> >
> >-----Original Message-----
> >From: everybody-bounces$##$orglist.net [everybody-bounces$##$orglist.net]
> >On Behalf Of Christopher Joseph Gorman
> >Sent: 13 December 2004 21:49
> >To: Jacobo Cruces; everybody$##$orglist.net; cjgorman$##$sas.upenn.edu;
> >thenextgenesis$##$gmail.com
> >Subject: Re: ORGLIST: Suggestions
> >
> >Mechanisms for name reactions, I believe, are the most useful reference
for
> >advanced students of organic chemistry. Good luck on your project. Let
me
> >know if you have any questions or need any further advice, All the Best,
> >
> >Chris J. Gorman
> >Undergraduate Class of 2005
> >University of Pennsylvania
> >
> >
> >> Dear all,
> >>
> >> In the past years we have made available for the community of organic
> >> chemists a number of documents in different formats which we believe
can
> >be
> >> of general interest: e-books on nomenclature, mechanisms, exercises,
> >> tables, etc.
> >>
> >> We are now collecting ideas for the next year's downloads, so we would
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> >> Best regards,
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> >> Dr. Jacobo Cruces
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> >"The nature of the truth is fundamentally biased by the nature of our
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> ------------------------------
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> Message: 2
> Date: Wed, 15 Dec 2004 21:42:08 +0100
> From: "stephanie" <roulle.stephanie$##$wanadoo.fr>
> Subject: ORGLIST: nucleophilic substitution
> To: <everybody$##$orglist.net>
> Message-ID: <000601c4e2e6$92d710a0$daa87d52$##$bertrandd4yjbz>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hello everybody,
> I have to do a nucleophilic substitution between a primary amine and a
mesylate of an alcohol. Actually I use 1eq of the mesylate alcohol and 2 eq
of the amine (1 eq as base and 1 eq for the reaction).
> I want to use only 1 eq of this amine but I need a base. The problem is
that I don't want to do elimination, only substitution because I have an
asymetry center on the carbon on beta position and I don't want to racemize.
> I tied triethylamine in toluene, but I haven't good result.
> If anybody can help me!!!
> Thanks.
>
>
> Stephanie
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> Message: 3
> Date: Wed, 15 Dec 2004 22:51:09 -0300 (ART)
> From: Jos? Barros <zerozero43$##$yahoo.com.br>
> Subject: ORGLIST: ketal synthesis
> To: everybody$##$orglist.net
> Message-ID: <20041216015109.11349.qmail$##$web60705.mail.yahoo.com>
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>
> Dear all,
>
> Did someone have problems to make a ketal of tartaric
> acid using 2,2-dimethoxypropane??
>
> I've tried the procedure of Org. Syn. (Annual Volume
> 68, page 92) but in fact, I obtained a kind of black
> product, I don't know if the product decomposes or
> polimerises.
>
> Best regards
> J.C. Barros.
>
>
> __________________________________________________
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> ------------------------------
>
> Message: 4
> Date: Wed, 15 Dec 2004 23:38:50 -0500
> From: "Ken Knott" <esprcorn$##$hotmail.com>
> Subject: ORGLIST: Deprotection of a trityl group
> To: everybody$##$orglist.net
> Message-ID: <BAY102-F301BDB8D77855ADAF5F2ADCBAE0$##$phx.gbl>
> Content-Type: text/plain; format=flowed
>
> I have having issues deprotecting a trityl group from an amine. According
> the the publsihed papers the deprotection should occur easily with an
acidic
> media. I have tried HCl, HBr, triflouroacetic acid, and others. Suffice
to
> say the deprotection does not occur.
>
> I have also tried sodium in methanol based on a paper. This made a mess
and
> did not work.
>
> Lastly I have tried a dehydrogenation with Pd/C catalyst 10%. This
appears
> to have worked though after a day at atomospheric pressure it appears to
> have only been about 10-20% effective. I work in an inorganic lab and
> dehydrogenation appartus is not readily available for increased pressures.
> I used a baloon.
>
> Can someone suggest possible other routes, an improved method for the
> dehydrogenation, or possibly suggest a better catalyst?
>
> Oh, and if someone can tell me why the deprotection isn't working with
> acids, I am curious as everything I've seen indicaies that it should be
very
> facile.
>
> Thanks,
>
> Ken
>
>
>
>
> ------------------------------
>
> Message: 5
> Date: Wed, 15 Dec 2004 20:56:10 -0800 (PST)
> From: Maringanti Krishna <maringanti9$##$yahoo.com>
> Subject: ORGLIST: Methyl Lithium-Lithium Bromide complex
> To: everybody$##$orglist.net
> Message-ID: <20041216045610.55683.qmail$##$web51505.mail.yahoo.com>
> Content-Type: text/plain; charset="us-ascii"
>
> Friends:
> Can any one give me Fieser or any other method for the preparation of 1:1
Methyl Lithium-Lithium Bromide complex in any solvent? I really appreciate
the help!
> Thanks,
> Krishna
>
>
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