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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: affa on April 28, 2008, 08:53:38 AM

Title: Methods to deprotect tert-butyl amides
Post by: affa on April 28, 2008, 08:53:38 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.
Title: Re: Methods to deprotect tert-butyl amides
Post by: russellm72 on April 29, 2008, 10:10:11 AM
Can I ask why is it on there?

R.
Title: Re: Methods to deprotect tert-butyl amides
Post by: affa on April 29, 2008, 12:02:48 PM
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?
Title: Re: Methods to deprotect tert-butyl amides
Post by: agrobert on April 29, 2008, 02:07:57 PM
Can you expose your compound to aqueous acidic conditions?
Title: Re: Methods to deprotect tert-butyl amides
Post by: affa on April 30, 2008, 11:52:44 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.