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Topic: Removal of Triethylamine or Pyridine  (Read 19190 times)

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Offline MasterChief

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Removal of Triethylamine or Pyridine
« on: May 17, 2013, 11:55:24 AM »
So I am doing an acid chloride coupling using standard conditions. (DCM, triethylamine). The issue is that on my compound there is a tertiary amine. So when I wash with dilute HCl to remove the triethylamine from the reaction, I also pull my compound into the aqueous layer.

One idea that I have is to use pyridine instead of TEA, so I can wash with CuSO4 to remove the pyridine during workup.

Does this seem feasible? Any other ideas to overcome this issue?
Thanks!

Offline opsomath

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Re: Removal of Triethylamine or Pyridine
« Reply #1 on: May 17, 2013, 12:31:05 PM »
TEA is pretty easy to remove using a rotovap if you turn up the bath and use patience. Alternatively, you can distill it off of your product.

The pyridine/copper sulfate thing was always a pain in the butt for me but some of my coworkers swore by it. At least it makes pretty colors.

If I had your workup to do, I'd use ether as the solvent (amines love DCM) and assuming your tertiary amine isn't too polar, wash something like 5x with water, then brine. Then I'd pull off the remaining TEA with vacuum (bp 90°C).

Also, just use 1.1 equivalent of TEA rather than an excess and filter off the TEA-HCl salt before workup.

Offline democanarchis

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Re: Removal of Triethylamine or Pyridine
« Reply #2 on: May 20, 2013, 11:26:25 AM »
I often work up TEA with 10% w/v CuSO4 aq, so beware, you could still end up pulling your compound into the aqueous. I'd second opsomath's recomendation of distilling it off, followed by something like a Kugelrohr distillation to get the last drop out.

Offline Dan

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Re: Removal of Triethylamine or Pyridine
« Reply #3 on: May 20, 2013, 12:23:37 PM »
TEA is very easy to remove on a rotavap connected to a decent diaphragm pump (10-15 mbar). Its bp is only 90 °C. I used to run TEA-doped columns for amine purification routinely and never had any issues getting rid of it at 30-40 °C. I'd just vac it off.
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Offline Babcock_Hall

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Re: Removal of Triethylamine or Pyridine
« Reply #4 on: May 20, 2013, 02:46:03 PM »
By coincidence, I read a paper from 1961 on the alkylation of cysteine.  When they tried to substitute pyridine for triethylamine, they did not see a reaction.  It pays to keep up with the literature.

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