solo
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Dakin-West Reaction.....
This is an old on going thorn that I can't seem to resolve , so I will post for some insight from the members.............solo
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Dakin-West Reaction.........
Here are some facts regarding Dakin-West reaction and how it can be applied to Phenylalanine. "When an amino acid is treated with an anhydride in the
presence of pyridine, the carboxyl group is replaced by an acyl group and the NH2 becomes acylated. This is called the Dakin-West reaction. The
mechanism involves formationof an oxazolone. The reaction sometimes takes place on carboxyl acids even when an amino group is not present . A number
of N-substituded amino acids , RCH(NHR' )COOH, give the corresponding N_alkylated products.
................................. " as stated on page 812 from 5th edition March's text.
Ref.
Buchanan, G.L.Chem.Soc.Rev.,1988,17,91-109
Allinger, N.L.; Wang, G.L. ; Dewhyrst, B.B., Org. Chem., 1974,39,1730
Note..........pyridine can be substituded with sodium acetate
Now the question is how to reduce the newly formed ketone at the former
COOH site so that it can be an aldehyde or an alcohol staying in a three carbon chain ........here is something I found,
I hit the books and tried to resolve the ketone removal of this equation and ran into some interesting material in March's 5th ed. page 318,
.....through some photochemistry ketones can be processed through type I cleavage in the Norrish Type I cleavage
HV
R'-CO-R -------> R'-CO- + R
However I've not taken it further but will get some references on the Norrish type I cleavage chemistry.
I've included a reference on Dakin West................
[Edited on 1-9-2006 by solo]
Attachment: The Dakin–West reaction.pdf (393kB)
This file has been downloaded 965 times
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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solo
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Here is some more info from the authors of the reaction..................solo
Reference Information
A GENERAL REACTION OF AMINO ACIDS. I & II
BY H. D. DAKIN AND RANDOLPH WEST.
Journal of Biological Chemistry, 1928
http://rapidshare.de/files/31606253/A__GENERAL__REACTION__OF...
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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Nicodem
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Solo, like usually I don't have an answer to your main question. Making an aldehyde out of a ketone like that one, in one step, is beyond my knowledge
and that Norish photocleavage seams pretty much useless in practice.
The Dakin-West reaction is a ketonization more known to the public in its use as an (in)famous method to form phenylpropan-2-one from phenylacetic
acid. But it works better with amino acids since the intermediate oxazolone has the C-H bond much more activated and is thus easily acylated.
Unless you necessarily want to prepare Ph-CH-CH(NHAc)-CHO in no less than two steps and unless it necessarily needs to be an acylamide you might
consider using the famous HCOOH/Ac2O formylation mixture that could potentially lead to Ph-CH-CH(NH-CHO)-CHO.
HCOOH/Ac2O forms the mixed formic and acetic acid anhydride (Ac-O-CHO) in situ which acts exclusively as a formylating reagent since the
formylic carbonyl is considerably more electrophilic than the acetylic one and thus reacts faster. However, since Ac2O would need to be in excess,
chances are that some of the concurrent N-acylation would happen, but the C-formylation of the oxazolone should be nearly exclusive over C-acetylation
as it is a more reversible reaction and thus allows for the thermodynamic product to form.
There are little chances that everything works but still it is the only thing I can propose without searching with Beilstein. Aldehydes are much more
reactive and prone to polymerizations and other unwanted reactions, but it might nevertheless work.
PS: Wasn't there already a thread with this exact topic somewhere?
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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solo
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Yes Nicodem, your memory serves you right, .............the thorn was embedded in me at the Hive , where I originally posted my
querry and have yet to make any real headway , however your proposal appears promising...............and you're right the Norrish type I cleavage
chemistry is reaching .....but nothing was ever accomplished whithout trying and searching .................solo
Note: Here is an interesting Clemmenson reduction without the polluting mercury that can be used to reduce the aldehyde or ketone to the hydrocarbon
found by aminorex over at drugs-forum ......solo
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Reduction of alkylarylketones to alkylbenzenes with zinc dust and hydrochloric acid: comparison with zinc amalgam reduction.
Vladimir N. Bulavka
8th International Electronic Conference on Synthetic Organic Chemistry. ECSOC-8. 1-30 November 2004.
http://www.usc.es/congresos/ecsoc/8/GOS/025/index.htm
[Edited on 1-9-2006 by solo]
[Edited on 1-9-2006 by solo]
Attachment: Clemminson%20method%20with%20zinc.pdf (109kB)
This file has been downloaded 2773 times
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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Drunkguy
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That's a good Clemmensen Red. Tar for the link.
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