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Author Topic: Derivates of imidazolium and benzimidazolium salts synthesis?  (Read 1467 times)

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mhanze

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Derivates of imidazolium and benzimidazolium salts synthesis?
« on: November 30, 2012, 05:28:50 AM »

Hey guys, I am working on a project which contains synthensis of compounds on picture, and I have huge trouble in quaternization od imidazole and benzimidazole rings, so I was wondering if maybe some of you have experience in that part od organic synthesis? I need a good condition for quaternization. I have tried with MeI in acetone for 24 hours in dark bottle and it doesent seem to be working :S
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discodermolide

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Re: Derivates of imidazolium and benzimidazolium salts synthesis?
« Reply #1 on: November 30, 2012, 05:31:01 AM »

You say it is not working. What do you get? Recovery of starting material or something else?
In other words can you account for all the mass in?
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mhanze

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Re: Derivates of imidazolium and benzimidazolium salts synthesis?
« Reply #2 on: November 30, 2012, 05:36:32 AM »

You say it is not working. What do you get? Recovery of starting material or something else?
In other words can you account for all the mass in?

The reaction of for example ethyl-chloroformate and imidazole is working fine, you get oily product which has carbonyl group and C(O)-N signal in IR spectrum...thats ok..but now I need to do a quaternization and that is not going well, when you mix CH3I with carbamate in acetone you should get two layers and white salt of imidazolium but nothing happent, so I need better way to do the quaternization without messing up other parts of the product.
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discodermolide

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Re: Derivates of imidazolium and benzimidazolium salts synthesis?
« Reply #3 on: November 30, 2012, 05:41:07 AM »

Yes, but do you recover the carbamate or not?
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mhanze

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Re: Derivates of imidazolium and benzimidazolium salts synthesis?
« Reply #4 on: November 30, 2012, 05:46:56 AM »

Yes, but do you recover the carbamate or not?

Nope, imidazolium salt should be used in enzyme inhibition research (acetylcholinesterase).
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Re: Derivates of imidazolium and benzimidazolium salts synthesis?
« Reply #5 on: November 30, 2012, 05:55:46 AM »

OK, but you are not forming the salt, correct?
What do you get out of the reaction, do you get starting materials back, or do you get decomposition?
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mhanze

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Re: Derivates of imidazolium and benzimidazolium salts synthesis?
« Reply #6 on: November 30, 2012, 05:57:48 AM »

OK, but you are not forming the salt, correct?
What do you get out of the reaction, do you get starting materials back, or do you get decomposition?

In acetone it just doesnt react, so you get mixture of carbamate, methyl-iodide and acetone
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discodermolide

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Re: Derivates of imidazolium and benzimidazolium salts synthesis?
« Reply #7 on: November 30, 2012, 05:58:48 AM »

Finally, thank you.
Have you tried any other solvents?
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Re: Derivates of imidazolium and benzimidazolium salts synthesis?
« Reply #8 on: November 30, 2012, 06:04:12 AM »

… so I need better way to do the quaternization without messing up other parts of the product.

Go on? Is the problem a reaction is occurring elsewhere?
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mhanze

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Re: Derivates of imidazolium and benzimidazolium salts synthesis?
« Reply #9 on: November 30, 2012, 06:06:01 AM »

Finally, thank you.
Have you tried any other solvents?

I have tried dry diethyl ether and now im waiting two days...well, i dont really know because there is no literature for these reaction conditions...i have one reference that could potentially be helpfull, but i cant get it, can you maybe download it for free? here it is the link: The reaction of benzimidazolium derivatives with superoxide
Nagata, Kazuhiro; Itoh, Takashi; Okada, Mamiko; Ohsawa, Akio
Tetrahedron, Volume: 52, Issue: 19, Pages: 6569-6580, Journal, 1996.
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Re: Derivates of imidazolium and benzimidazolium salts synthesis?
« Reply #10 on: November 30, 2012, 06:09:03 AM »

Soliciting literature is not allowed.
However, I would try a solvent like DMF.
You just said "so I need better way to do the quaternization without messing up other parts of the product."
So something else is happening?
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mhanze

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Re: Derivates of imidazolium and benzimidazolium salts synthesis?
« Reply #11 on: November 30, 2012, 06:11:29 AM »

… so I need better way to do the quaternization without messing up other parts of the product.

Go on? Is the problem a reaction is occurring elsewhere?

Carbamate synthesis is really not a big deal, the products are sensitive and I keep them in fridge...
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mhanze

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Re: Derivates of imidazolium and benzimidazolium salts synthesis?
« Reply #12 on: November 30, 2012, 06:13:22 AM »

Soliciting literature is not allowed.
However, I would try a solvent like DMF.
You just said "so I need better way to do the quaternization without messing up other parts of the product."
So something else is happening?

So the solution is another solvent, hmmm, what do you think how long does it take to complete quaternization, should I just leave it in fridge for couple of days?
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discodermolide

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Re: Derivates of imidazolium and benzimidazolium salts synthesis?
« Reply #13 on: November 30, 2012, 06:17:03 AM »

I did not say that the solution is to use another solvent. I asked have you tried other solvents.
And why is it in the fridge, try at room temperature.
Usually you follow the course of a reaction by TLC or other analytical methods. This should tell you when it is complete.
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mhanze

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Re: Derivates of imidazolium and benzimidazolium salts synthesis?
« Reply #14 on: November 30, 2012, 06:24:31 AM »

I did not say that the solution is to use another solvent. I asked have you tried other solvents.
And why is it in the fridge, try at room temperature.
Usually you follow the course of a reaction by TLC or other analytical methods. This should tell you when it is complete.

Ok, but you can clearly tell if quaternization is complete or even happening, Ill try some other solvents and room temperature with no light acces. Thanx for help ;)
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