dormouse (Member)
04-23-00 05:21
No 108760
      Amino-mercuration -Siegfried  Bookmark   


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Siegfried
Member   posted 07-22-99 01:05 PM          
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Hi ,
Two year ago i dreaming about a direct amination of olefin .
The old process in my dream was oxymercuration to alkohol , then tosylation , then amination , in my dream this process gave better yield than classic nucleophile substitution of alkyl halide with amine , since tosylate don't give a lot of elimination to the stabilized methyl-styrene and it has better cinetic .
But i have a new dream : direct amino- mercuration ... But it was a nightmare because my methylamine ( wich was in methanol ) was complexed by the mercury ion and this complex was a really bad nucleophile and the methanol add instead the methylamine giving 1-phenyl-2-methoxy-propane !!
So what can i do for destroying this complex , i have read about temperatur of 60C , how it is ??
Excuse my rusty english !
 
ReFlux
Member   posted 07-22-99 01:49 PM          
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I don't see how the methanol would have added across the double bond w/o first complexing w/ the mercury. The perferred solvent for amino-mercuration is THF, since it doesn't react w/ Hg salts. No clue on what you got or what to do with it. But I do have some notes on amino-merc if your intersted.
-ReFlux


psychokitty
Member   posted 07-22-99 07:51 PM          
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There is a article published in Journal of Organic Chemistry detailing the synthesis of several N-substituted amphetamines using the amino-mercuration demercuration technique. As precursors, they used several ring substituted allylbenzenes. The amines used were varied but some, like ethylamine, were in aqueous solution, and even so, there was no competing hydroxymercuration reaction taking place. It is a really neat article and seems to be proof that the amino-mercuration demercuration of safrole might indeed be viable. Oh, I'm afraid I don't have the exact date the article was published, but if you go volume by volume between 1975 and 1985, you'll find it. Check out the index where "aminomercuration" should be listed.
Good luck.

--PK


Osmium
Member   posted 07-23-99 03:54 AM          
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JOC 44, 20, 3581 (1979) ?
 
Siegfried
Member   posted 07-23-99 01:11 PM          
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The methanol is nucleophil , so it can attack at the carbocation , there is a lot of procedure for synthesis of alkoxy product using alkohol and HgAc2 .
My solvent was THF but the methanol came from my methylamine .
I tried another amino-mercuration using piperidine instead MeNH2-MeOH , it has worked but needed a long time ( the normal oxymercuration process take only some minute ) . In addition there was a non negligeable part of acetate product , that's mean the acetate ion is enough nucleophile to compete the amino-mercurial complex .
There is other procedure using Hg(NO3)2 ( anhydrous ) and Hg(ClO4)2 but i don't tried it .
I know other route with MeCN or phosphoramidate , but no direct route .
What about this procedure for amino- mercuration of allylbenzene you spoke ? what refs ? what solvent (THF) ? HgAc2 ? nitrate ? perchlorate ? yield ? and reaction time ? what is the source of amine ( MeNH2.HCl ) because methanol and water will compete ?
The work-up is important , because the aziridium intermediate can conduct to the anti-markownikov product
thanks for the answer .
 
ReFlux
Member   posted 07-23-99 03:43 PM          
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Water will not compete in amino-merc. reactions using THF as solvent. MeNH2 is used in aq. sol'n. in this reaction. I've played around with this reaction several times and always its the reduction step that messes up. I found a paper on using PTCs to aid in borohydride reduction, this looks promising, but would involve first isolating the organomercurials and thus would be a two-pot shot.
-ReFlux


Siegfried
Member   posted 07-25-99 06:56 AM          
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I think in your procedure there is special condition of reaction ( perhaps heating ) for decreasing the binding of mercury and amine , so what are the condition of reaction ? and the nature of mercury salt ?
 
Osmium
Member   posted 07-26-99 05:21 AM          
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Check that ref I mentioned last week. I think it worked best with perchlorate, and water didn't interfere in this reaction.
Or is it the wrong ref? Anybody crrect me if I'm wrong.


Siegfried
Member   posted 07-26-99 12:41 PM          
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Ok , thank u , i will check it soon .
 
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