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Topic: Electron poor amine silylation  (Read 5353 times)

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Offline 408

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Electron poor amine silylation
« on: March 24, 2012, 06:19:52 PM »
I have a very very electron poor primary amine.  Refluxing with Me3SiCl, HMDS or PhN(SiMe3)CONHPh all fail at protecting it.

The amine must be protected toward a grignard reagent.  Any suggestions for silylation reagents and/or alternative protection methods?

thanks,
408

Offline OC pro

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Re: Electron poor amine silylation
« Reply #1 on: March 25, 2012, 02:05:38 PM »
Need more structural details. What kind of Grignard is it? Sp2- or sp3?

Offline Honclbrif

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Re: Electron poor amine silylation
« Reply #2 on: March 25, 2012, 03:24:33 PM »
If your Grignard isn't anything too special, you might be able to let the amine just eat a couple of equivalents and have the excess perform the addition.
Individual results may vary

Offline 408

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Re: Electron poor amine silylation
« Reply #3 on: March 25, 2012, 03:57:59 PM »
sp3 grignard, that is easy to make and cheap. 

However silylation is also necessary for solubility.  the compound has strong intermolecular forces and is thus insoluble in most solvents (best in MeCN, DMSO), so would be insoluble in THF or Ether...

There are two amines in the molecule and two equivalents must add elsewhere.  Will letting the amines eat 2 equiv make the molecule too negative for the grignard to then attack? (also, won't the grignard reacting with an amine give a -NHMgBr nitrogen grignard which could then attack where I want my reagent to attack, but being electron poor would mean my grignard would react quicker at the active site...)

Maybe I just add solid amine to ethereal grignard in excess and see what happens.... :-\

Both the grignard reagent and what it is attacking is non-traditional (this is not forming a C-C bond...)

Offline Honclbrif

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Re: Electron poor amine silylation
« Reply #4 on: March 25, 2012, 04:46:27 PM »
If you're doing some weird stuff with the grignard you'll probably have to be more careful.

I've had good luck with this reference: J. Org. Chem., 1982, 47 (20), pp 3966–3969.

It contains some jacked-up crazy TMS transfer reagents.
Individual results may vary

Offline Honclbrif

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Re: Electron poor amine silylation
« Reply #5 on: March 25, 2012, 09:27:25 PM »
Addendum:

My favorite catalyst from the paper is simply saccharin. Its easy to use and cheap. In fact, I did a test reaction with material I extracted from those pink sweetener packets which languish next to the coffee machine.
Individual results may vary

Offline 408

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Re: Electron poor amine silylation
« Reply #6 on: March 26, 2012, 04:28:51 PM »
If you're doing some weird stuff with the grignard you'll probably have to be more careful.


Hope you are wrong ;)  Waiting for ms data now.  just big excess grig.  something happened.  Not sure what yet...

Offline Honclbrif

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Re: Electron poor amine silylation
« Reply #7 on: March 27, 2012, 10:06:13 AM »
I hope it was something good!
Individual results may vary

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