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Author Topic: Methods to deprotect tert-butyl amides  (Read 4567 times)

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affa

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Methods to deprotect tert-butyl amides
« on: April 28, 2008, 02:53:38 AM »

I am working to cleave the N-bound tert-butyl group from a tertiary amide (aliphatic one) to regenerate a N-H in secondary amide.

I have tried using trifluoroacetic acid (TFA) or even trifluoromethanesulfonic acid (TfOH) under refluxing dichloromethane conditions (~ 39 oC). However, the tert-butyl group is unreactive at all.

Can anyone suggest alternative conditions to deprotect a tert-butyl from amides? Thank for your attention.
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russellm72

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Re: Methods to deprotect tert-butyl amides
« Reply #1 on: April 29, 2008, 04:10:11 AM »

Can I ask why is it on there?

R.
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affa

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Re: Methods to deprotect tert-butyl amides
« Reply #2 on: April 29, 2008, 06:02:48 AM »

tert-butyl tertiary amide was prepared to control the amide rotamer by forcing another alkyl substituent (reaction site) "anti-" to the amide carbonyl. Otherwise, the alkyl substituent would be "syn-" to the amide carbonyl, which cannot lead to desired reactions.

Do you have any idea to cleave this bulky group?
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agrobert

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Re: Methods to deprotect tert-butyl amides
« Reply #3 on: April 29, 2008, 08:07:57 AM »

Can you expose your compound to aqueous acidic conditions?
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In the realm of scientific observation, luck is only granted to those who are prepared. -Louis Pasteur

affa

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Re: Methods to deprotect tert-butyl amides
« Reply #4 on: April 30, 2008, 05:52:44 PM »

coz I think protic acid in non-aqueous medium is more "acidic" than that in aqueous, where the acid protons mostly occupied by aqueous but not to protonate the amide substrates.
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