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Topic: Tosylation reaction  (Read 9537 times)

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Offline chepda06

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Tosylation reaction
« on: November 13, 2010, 05:40:47 AM »
I'm trying to make the tosylate of dimethylaminoethanol, but I am having trouble isolating the product as I find it degrades following work-up.  Can anybody suggest any work-up conditions which will avoid degradation?  Currently, I'm doing the reaction in THF using triethylamine as base.  When the reaction is complete, I add water to dissolve the salt formed and then wash with ethyl acetate.  TLC analysis of each organic washing shows that the product is still there, but when I remove the solvent in vacuo I am only left with starting material.  Thanks in advance.

Offline movies

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Re: Tosylation reaction
« Reply #1 on: November 13, 2010, 10:41:23 AM »
Instead of adding water to dissolve the salts, try just filtering (washing with THF) and then wash the filtrate with aqueous sodium citrate solution (to wash out remaining Et3N), then dry and concentrate the organic layer.  I would expect the product to be fairly pure.  I wouldn't expect your product to be very volatile, but perhaps use some care when you concentrate the organics.

Offline chepda06

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Re: Tosylation reaction
« Reply #2 on: November 13, 2010, 05:18:27 PM »
Thanks for your help.  Would washing the filtrate with sodium carbonate solution work just as well?

Offline discodermolide

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Re: Tosylation reaction
« Reply #3 on: November 14, 2010, 09:20:47 AM »
I'm trying to make the tosylate of dimethylaminoethanol, but I am having trouble isolating the product as I find it degrades following work-up.  Can anybody suggest any work-up conditions which will avoid degradation?  Currently, I'm doing the reaction in THF using triethylamine as base.  When the reaction is complete, I add water to dissolve the salt formed and then wash with ethyl acetate.  TLC analysis of each organic washing shows that the product is still there, but when I remove the solvent in vacuo I am only left with starting material.  Thanks in advance.

You are only protonating the dimethylamine. Note if you do ever get the tosylate using this method it will give you an aziridine

Try using a phthalimido as protecting group
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Offline NL-bucky

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Re: Tosylation reaction
« Reply #4 on: November 26, 2010, 05:39:15 AM »
Try solid state: grind with TsCl and K2CO3, heat in oven, extract with ether. Something like
DOI: 10.1016/j.tet.2007.03.083

Offline nox

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Re: Tosylation reaction
« Reply #5 on: January 09, 2011, 03:14:25 PM »
You are only protonating the dimethylamine. Note if you do ever get the tosylate using this method it will give you an aziridine

Try using a phthalimido as protecting group


I don't think the aziridine thus formed would be very stable, simply because the nitrogen would be quaternary, and it would just spring right open given the opportunity.

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