April 17, 2021, 11:03:51 PM
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Topic: work-up following deacetylation of aromatic esters  (Read 1160 times)

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Offline rolnor

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Re: work-up following deacetylation of aromatic esters
« Reply #15 on: February 08, 2021, 10:58:49 AM »
Thats true, para will not be a problem if not the phenylring itself is charged in some way.

Offline Babcock_Hall

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Re: work-up following deacetylation of aromatic esters
« Reply #16 on: February 16, 2021, 09:26:05 AM »
Just a quick update, our first attempt had some glitches which reduced yield, and we repeated the deacetylation.  This week we will purify the combined products and see what we have.

Offline rolnor

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Re: work-up following deacetylation of aromatic esters
« Reply #17 on: February 16, 2021, 12:29:40 PM »
How does it look on TLC?

Offline Babcock_Hall

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Re: work-up following deacetylation of aromatic esters
« Reply #18 on: February 16, 2021, 01:36:20 PM »
The product ran more slowly than the starting material on TLC, with the solvent being 3% acetone in DCM.  For a column 3% acetone is not polar enough to move the product much, but 6% is looking roughly right (the Rf was about 0.32).
EDT
Removal using hydrazine is probably a fine method, but if I had to start from scratch, I might use ammonia in methanol.
« Last Edit: February 16, 2021, 02:17:25 PM by Babcock_Hall »

Offline rolnor

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Re: work-up following deacetylation of aromatic esters
« Reply #19 on: February 16, 2021, 02:05:10 PM »
That sound good. If you dipp the plate in 0.5%KMnO4 it should give strong staining compared to the diacetylcompound.

Offline Babcock_Hall

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Re: work-up following deacetylation of aromatic esters
« Reply #20 on: February 16, 2021, 02:18:56 PM »
Do I understand correctly that the phenol-type groups gives more reaction with KMnO4 than the acetylated phenols?  I was unaware of that.

Offline kriggy

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Re: work-up following deacetylation of aromatic esters
« Reply #21 on: February 17, 2021, 04:04:03 AM »
Possibly due to oxidation to quinone(s) which is blocked when acetylated? Also, FeCl3 is selective stain for phenols giving gray ish spots on yellow/orange background IIRC.

Do you need to run the collumn? Dont know the structure but phenoxide could be water soluble so you can get rid of the remaining organics just by dissolving it in basic water and extract with organics, then acidify and maybe it precipitates or get extracted again.

Offline rolnor

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Re: work-up following deacetylation of aromatic esters
« Reply #22 on: February 17, 2021, 08:59:30 AM »
Yes, phenols stain KMnO4 very much, esters does not.

Offline Babcock_Hall

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Re: work-up following deacetylation of aromatic esters
« Reply #23 on: February 24, 2021, 09:39:41 AM »
We used d6-acetone as our NMR solvent for the silica-purified material.  In retrospect my choice of solvent was not ideal; residual water is in the vicinity of the acetyl methyl groups, and the phenolic-OH signals were not strong.  There was a huge roll with an integral of less than one that may or may not have been a phenolic -OH.  The carbon NMR was a cleaner experiment; I have only glanced at it, but there is no sign of either carbon of an acetyl group.  Tentatively, I would say that the method was successful.  We may make up a sample in a different NMR solvent, such as DMSO.  Chloroform would be a challenge, but we might be able to get enough material into solution for 1H NMR only.  Obtaining MS data is not trivial for us right now, but it may become much more routine in a few months.
EDT
Thanks to all.  Chemical Forums is a great resource for us!
« Last Edit: February 24, 2021, 11:13:13 AM by Babcock_Hall »

Offline rolnor

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Re: work-up following deacetylation of aromatic esters
« Reply #24 on: February 24, 2021, 10:53:38 AM »
Great!

Offline Babcock_Hall

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Re: work-up following deacetylation of aromatic esters
« Reply #25 on: March 02, 2021, 09:38:01 AM »
One more follow-up:  I was able to get enough material into CDCl3 for 1H NMR, but the signal-to-noise ratio was low.  I see two candidates for the two Ar-OH hydrogens, and there is little to nothing where the acetyl methyl groups would be.  Again, thanks to everyone here.

Offline Babcock_Hall

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Re: work-up following deacetylation of aromatic esters
« Reply #26 on: March 24, 2021, 09:50:31 AM »
A very preliminary result suggests that our product has the desired biological effect (we have a long way to go).  I am very grateful for the advice received in these threads.

Offline rolnor

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Re: work-up following deacetylation of aromatic esters
« Reply #27 on: March 24, 2021, 12:02:47 PM »
Great!

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