ORGLIST: RE: Everybody Digest, Vol 6, Issue 8

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From: marut shah (marutshah5$##$hotmail.com)
Date: Fri Mar 11 2005 - 10:08:15 EST


Dear Maneesh
You can use nitrobenzene or such non polar sovent as reaction medium
alongwith triethylamine as catalyst. One can also try out dimethyl aniline
in a catalytic amount.
Marut Shah

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>Subject: Everybody Digest, Vol 6, Issue 8
>Date: Thu, 10 Mar 2005 12:02:48 -0500 (EST)
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>Today's Topics:
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> 1. *seemingly* tough o-alkylation of vanillin (Maneesh Yadav)
>
>
>----------------------------------------------------------------------
>
>Message: 1
>Date: Wed, 9 Mar 2005 18:43:48 -0800
>From: "Maneesh Yadav" <yadavm$##$scripps.edu>
>Subject: ORGLIST: *seemingly* tough o-alkylation of vanillin
>To: <everybody$##$orglist.net>
>Message-ID: <6FC7A54A7C4DD440810236C7432A436075F2D2$##$jcsg-ex1.jcsg.edu>
>Content-Type: text/plain; charset="iso-8859-1"
>
>Dear All,
>
>I am having a little problem with the o-alkylation of vanillin with
>bromomethane sulfonate and was hoping I could solicit a little practical
>advice.
>
>Here is ascii, just to be clear:
>
>
> (K2CO3, KOH)
>Vanillin---OH + Br-CH2-SO3 Na ----> Vanillin---O-CH2-SO3
>
>
>
>
>Iíve tried running high concentrations/excesses sulfonic acid in water to
>no avail. There is a published alkylation of a larger phenol by
>bromomethane sulfonate in DMF 132C, which didnít work for me.
>
>I am concerned about the quality of starting material which was made from
>CH2Br and sulfite(J Med Chem., 1987, Vol. 30, No . 12, pg. 2236), but it is
>a difficult thing to really test.
>
>There is an example of using microwaves for making aryloxymethanesulfonates
>here (free link):
>
>http://www.rsc.org/CFCart/displayarticlefree.cfm?article=8%2D9%223%24%5D2%5CB%218%27%5D%5CY%28%3E%5C%23%5B4%5DP0S7%2C%3D29%23%3C%0A
>
>this is exactly what I need (and it should only be better using bromo vs.
>chloro), so far stuff tends to just smoke and char. I tried in a
>conventional microwave and in one where I could apply accurate
>powerlevel/temp/pressuresÖbut no luck.
>
>There is a longer route to generate the alkyl chloride on the phenol, and I
>think I may have some product, but it has more steps and purifications,
>analogous to what was done here (free link):
>
>http://www.biochem.wisc.edu/kiessling/lab/pdfs/2002.young.AngewChemInt.pdf
>
>I suspect what is happening in the microwave case is more of the result of
>a vanillin melt rather than microwaves, as described here (free link):
>http://frigo.ath.cx/chemistry/me3po4.html
>
>I did give this a try (to 150C in oil bath), but I still canít get my hands
>on a mechanical stirrer, so I am having trouble with this. Gram quantities
>of vanillin donít really seem to melt into a liquid, gunky solid just tends
>to get stuck on the side on the round bottom flask (especially with the
>sulfonic acid reactant and dry K2CO3/KOH) with a magnetic stirrer.
>
>I suspect that the reaction is rate limited by the fact that you have to
>bring a phenolate and a sulfonic acid together, and the transition state
>suffers from a large amount of charge charge repulsion.
>
>Do you have any advice at all (words of encouragement happily accepted)? I
>have a feeling I can get the melt to eventually work, but I need to find
>the right apparatus. If you have ever done something analogous or might
>have a little tip or insight, it would be most greatly appreciated.
>
>Best,
>Maneesh
>
>
>------------------------------
>
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>End of Everybody Digest, Vol 6, Issue 8
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