Mailinmypocket
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Coumarin synthesis
I'm thinking of trying the synthesis of coumarin as detailed in this paper, and figured I would share the paper in case anyone else wants to try it
out:
http://www.pjps.pk/CD-PJPS-23-4-10/Paper-16.pdf
The nice part is that it does not use any acetic anhydride which is relatively hard to come by.
This page has a write up done by somebody who seems to have done the exact procedure scaled down, but did not reference the source:
http://users.jyu.fi/~juhesiit/coumarin.html
Ill report back on the outcome later on if all goes well 
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kavu
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That someone happens to be me. IIRC I used Vogels guidelines for most parts of the preparation.
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Mailinmypocket
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Quote: Originally posted by kavu  |
That someone happens to be me. IIRC I used Vogels guidelines for most parts of the preparation. |
Very nice! Then I have a question for you, for the steam distillation did you run a source of steam through the mixture or did you simply heat the
flask and replace water as it distilled off?
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kavu
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Either one works, for simplicity I just added hot water to the boiling mixture.
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Mailinmypocket
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Sounds good, I will try that as well as I'm not feeling like doing the whole steam setup. I couldn't tell how you did it as my browser isn't
displaying the images on your page.
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mr.crow
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Sounds like a good project.
There is an excellent thread by Klute where he makes salicylaldehyde using a different method. Reimer-Tiemann would be interesting to try.
Yeah you can just add water and boil that for steam distillation
[Edited on 21-2-2013 by mr.crow]
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kristofvagyok
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I have an old book: Praktikum der organisch-präparativen pharmazeutischen Chemie what also describes this reaction, with a little difference: it uses
acetic-anhydride instead of glacal acetic acid, because the Perkin reaction needs this.
As far I know it won't work really well with acetic acid. Even with Ac2O it has a little, 37% yield for the coumarin, according to the German book.
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Mailinmypocket
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I was thinking the yield was going to be low also since this was the first time I came across this reaction being done with anhydrous sodium acetate
(hence why it caught my interest) Just a bit concerned about how much salicylaldehyde I will need to make given the grim yield predictions...I don't
want to burn through a bunch of phenol if the end result is almost nothing.
Kavu, did you happen to weigh the crude product and determine the yield?
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kavu
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The yield is really low, there were visible amounts of product but not enough for any proper use.
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Vargouille
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According to the paper, yields varied from about 5-10% for the glacial acetic acid/ sodium acetate method.
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Nicodem
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Mailinmypocket, if you just want to do some heterocyclic chemistry and you do not specifically want coumarin, I would rather direct you toward the
Rap-Stoermer condensations to obtain 2-acyl benzofurans. Can you obtain or prepare any alpha-halo carbonyl compounds such as haloacetic acids and
their esters, phenacyl halides or other haloketones? Most of the products are crystalline solids, so that the isolation and purifications is simple
and does not require chromatography.
If you don't have any of these, you can try the synthesis of 2-acetylbenzofuran by the condensation of salicyladehyde with chloroacetone in acetone
with K2CO3 as the base. The nice thing about it is that a presumably sufficiently pure solution of chloroacetone in acetone is
easily prepared by the chlorination of acetone with trichloroisocyanuric acid with less than 1 mol% of sulfuric acid as the catalyst. The cyanuric
acid that forms, nearly quantitatively precipitates and can be filtered off. The reaction is simple as long as you follow exactly the patent
instructions and don't scale up (you can UTFSE to find the patent number and discussions). Let me know if you need assistance in finding references
about the condensation.
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Mailinmypocket
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| Quote: Originally posted by Nicodem | Mailinmypocket, if you just want to do some heterocyclic chemistry and you do not specifically want coumarin, I would rather direct you toward the
Rap-Stoermer condensations to obtain 2-acyl benzofurans. Can you obtain or prepare any alpha-halo carbonyl compounds such as haloacetic acids and
their esters, phenacyl halides or other haloketones? Most of the products are crystalline solids, so that the isolation and purifications is simple
and does not require chromatography.
If you don't have any of these, you can try the synthesis of 2-acetylbenzofuran by the condensation of salicyladehyde with chloroacetone in acetone
with K2CO3 as the base. The nice thing about it is that a presumably sufficiently pure solution of chloroacetone in acetone is
easily prepared by the chlorination of acetone with trichloroisocyanuric acid with less than 1 mol% of sulfuric acid as the catalyst. The cyanuric
acid that forms, nearly quantitatively precipitates and can be filtered off. The reaction is simple as long as you follow exactly the patent
instructions and don't scale up (you can UTFSE to find the patent number and discussions). Let me know if you need assistance in finding references
about the condensation. |
I forgot about this thread, sorry for the delay in responding. I have decided to drop the coumarin synthesis at the moment because, as you suspected,
I am only exploring heterocyclic chemistry. Coumarin is not a necessity.
I am seriously considering your suggested synthesis of 2-acetylbenzofuran, as I don't have any haloacetic acids on hand at the moment. The first step
right now is preparing some salicylaldehyde. Once that is completed I may hit you up should I need assistance finding references, thanks!
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