zephler
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Reductive amination of ketones with Zn in acetic acid!
this girl I used to date showed me this paper a few weeks ago, as she is researching phrams at the U (http://www.scribd.com/doc/31475521/WO-2009-116084-Method-for...) - and I was quite surprised to read that these guys reduced their ketone
(piperidinone) using just Zn and Acetic acid, then went on to do the Sn2 of a halo-phenyl group with the above product using - get this - 100% NaOH at
120 C! WOW! Those are some crazy harsh conditions!!!! I am honestly surprised that the molecule can withstand that crazy treatment!!!! Now a short
question if you are still with me on this - my cousin said he went to school with some chemist that tried this- he said that after the Zn reduction ,
the Zn was of course filtered and the solution was neutralized . Upon neutralization a large white cloud of precipitate formed which is admittedly a
bit different than what I have ever seen - usually an oil of whatever freebase it is you are looking for forms. Anyways, this precipitate is a white
chalky powder - Definitely NOT the colorless needles that authors claim it to be. I am trying to determine just what this powder was. Sodium
acetate? Seems likely as there is a whack load of acetic acid in there, and they just neutralized with NaOH - but this should wash way in the water
layer?!?! Now, another possibility might be ZnO or Zn(OH)2, as the Zn was Zn dust, and some got pulled into solution since the solution was acetic
acid. But ZnO and Zn(OH)2 are water soluble right? Well, I will keep you updated
[Edited on 4-12-2010 by zephler]
[madscientist: Fixed typo in thread title - it was driving me crazy.]
[Edited on 8-12-2010 by madscientist]
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Random
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zno and zn(oh)2 aren't water soluble
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TheOrbit
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i don't like patents , there is always something vague
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chemrox
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The N-alkylation of piperidones with halo-alkanes is very slow and doesn't go except in strong base. Look very carefully at that 100%. It may mean
something other than what you think. When I read this last year I gained some insight into working with alkyl halides and piperidines: keep the pH
> 14. Reductive ams sometimes do go in Zn/AcOH. I haven't tried it with an alkyl-piperidone but it's an intriguing idea.. very GREEN.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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woelen
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Thread Moved
5-12-2010 at 12:02 |
woelen
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Thread moved, this is organic chemistry.
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jon
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i think that was the whole impetus behind the scheme reductively aminate the piperidone first then alkylate it then acylate because piperidones and
strongly basic evirons tend to self polymerize so you see that method is a gem and very green.
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zephler
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reductive amination with Zn and acetic acid?
has anyone attempted this reaction? A bifunctional molecule (with an amine and a ketone group, the ketone being the one that we are after) - [0.1
mol] was mixed with [0.25 moles] of aniline, to which GAA (as a solvent - so around 2 moles) was added as a solvent. To this mixture was added 0.4
moles of Zn powder and the contents were stirred for 12 hours at room temp, and then for 12 hours at 70-80C. The mixture was cooled, diluted heavily
with water and poured trough filter to remove the Zn. The sol'n was made very basic (13+) with NaOH, at which point large clouds of whit precipitate
formed. The solution was filtered to leave a chalky white power behind - the product that was sought is actually colorless needles - far from this
"stuff". Tried to recrystalize with acetone as suggested, but the white precipitate does not even dissolve - WHAT IS IT? I have my suspicions of ZnO,
Zn (OH)2, Zn acetate - oh wait this is a basic solution, so would the acetate even exist at this ph? Furthermore, it would seem that quite a large
amount of Zn actually dissolved during the heating in acetic acid step. So does anyone have experience with this reaction? Anyone want to hazard a
guess on the white precipitate?
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madscientist
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Threads Merged
7-12-2010 at 20:18 |
jon
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no, but at this point i would extract it.
and wash all the insolubles with the appropriate extraction solvent too.
also search the authors in chem abs. for that year and previous years you might gleen more details out of that.
[Edited on 8-12-2010 by jon]
[Edited on 8-12-2010 by jon]
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zephler
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Quote: Originally posted by chemrox  | | The N-alkylation of piperidones with halo-alkanes is very slow and doesn't go except in strong base. Look very carefully at that 100%. It may mean
something other than what you think. When I read this last year I gained some insight into working with alkyl halides and piperidines: keep the pH
> 14. Reductive ams sometimes do go in Zn/AcOH. I haven't tried it with an alkyl-piperidone but it's an intriguing idea.. very GREEN.
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Thank you for your feedback - I way over thought this - it's simply 1 gram of NaOH to 1 mL of water
[Edited on 11-12-2010 by zephler]
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zephler
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| Quote: Originally posted by jon | no, but at this point i would extract it.
and wash all the insolubles with the appropriate extraction solvent too.
also search the authors in chem abs. for that year and previous years you might gleen more details out of that.
[Edited on 8-12-2010 by jon]
[Edited on 8-12-2010 by jon] |
Thank you for your suggestion - I will suggest that route to her - Jon, unfortunately I do not have access to Chem Abstracts or Sci Finder here  Please disregard the 100% NaOH thingy I am over thinking things too
much
[Edited on 11-12-2010 by zephler]
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