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Topic: TBS Protection  (Read 15905 times)

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Offline Swerning

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TBS Protection
« on: March 14, 2007, 05:40:28 PM »
Hi, I'm trying to protect an hydroxyl group on a ring as its silyl ether (TBS group), but i'm having no joy, also the hydroxyl group has a small alkenyl chain alpha to it and they are cis to one another

I tried the standard reaction of TBDMSCl, imidazole, DMF but this just gave unreacted starting material. I was thinking instead to try TBDMSCl, Et3N and DMAP or use the more reactive TBDMSOTf.

Any thoughts??

Offline Dan

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Re: TBS Protection
« Reply #1 on: March 15, 2007, 05:29:26 AM »
I had a stubborn neopentyl OH I wanted to silylate a few months ago. I got my best yields using TBDMSCl and using pyridine as the solvent/base, stir at RT overnight. I don't like imidazole because it's a pain to get rid of.

A post doc in the group had a very stubborn OH which me managed to protect by using something like 3 eq TBDMSCl, 5 eq imidazole, very concentrated in DMF and heated to 100 degrees C.
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Offline movies

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Re: TBS Protection
« Reply #2 on: March 15, 2007, 12:04:16 PM »
As you suggested, DMAP is a good additive here.  Silyl triflates are okay, but they sometimes cause some other problems depending on what else you have in your molecule.

A guy in our lab had some crazy conditions with TBSCl and AgNO3.  He swore by them!

Offline wintermute

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Re: TBS Protection
« Reply #3 on: March 20, 2007, 06:28:11 AM »

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