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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: 408 on December 12, 2011, 09:29:39 AM

Title: Amine protecting groups
Post by: 408 on December 12, 2011, 09:29:39 AM

Hi,

I have a heterocyclic amine which I need to protect towards oxidizing conditions.  Any recommended protecting groups?  It needs to survive aqueous acidic peroxide based oxidation reagents.

Thanks,
408

Title: Re: Amine protecting groups
Post by: Honclbrif on December 12, 2011, 10:42:28 AM

You can probably get away with Fmoc

Title: Re: Amine protecting groups
Post by: OC pro on December 12, 2011, 04:00:30 PM

If it is only slightly acidic: Boc boc boc boc boc boc...one of my favorites. ;D
Survives generally even acetic acid at room temperature.

Title: Re: Amine protecting groups
Post by: Oxime on December 12, 2011, 10:50:25 PM

Cbz (Benzyloxy carbamate) protecting group is stable to even highly acidic conditions (TFA at room temp, 2-4 hours) but I'm not sure about its stability under oxidative conditions.

Title: Re: Amine protecting groups
Post by: Honclbrif on December 13, 2011, 12:21:31 PM

Depending on what's being oxidized, it may all be undone when removing the Cbz.

Title: Re: Amine protecting groups
Post by: fledarmus on December 13, 2011, 01:59:04 PM

Echo what Honclbrif said - you may need to select your deprotection conditions carefully. Cbz is frequently removed by reduction, which may also reduce the group you just oxidized.

Title: Re: Amine protecting groups
Post by: 408 on December 13, 2011, 04:33:36 PM

I will give the above a shot!  Thanks!

Title: Re: Amine protecting groups
Post by: Åke on December 27, 2011, 09:44:54 PM

Quote from: Honclbrif on December 12, 2011, 10:42:28 AM

You can probably get away with Fmoc

Is using Fmoc really getting away with it? 408, have you considered good old acetyl? Trifluoroacetyl is another, very useful protecting group for amines, it's really easy to attach and to hydrolyze - I'd give it a shot. Next on the list would be tosyl and analogs. I'd consider fancy protecting groups only if the simpler ones would prove unsuitable. What ya reckon, bad boys?  8)

Title: Re: Amine protecting groups
Post by: 408 on December 29, 2011, 06:42:31 AM

I protected with pthalic anhydride ;)  cheap and easy. 
And far more stable than the others, its gotta survive hypofluorous acid ( Did I mention I love my chemistry?)

Title: Re: Amine protecting groups
Post by: Åke on December 29, 2011, 05:54:59 PM

Quote from: 408 on December 29, 2011, 06:42:31 AM

I protected with pthalic anhydride ;)  cheap and easy. 
And far more stable than the others, its gotta survive hypofluorous acid ( Did I mention I love my chemistry?)

That's interesting, I didn't suggest phtalimide earlier since I assumed that your amine wasn't a primary one - based on your earlier post:

Quote from: 408 on December 12, 2011, 09:29:39 AM

Hi,

I have a heterocyclic amine which I need to protect towards oxidizing conditions.  Any recommended protecting groups?  It needs to survive aqueous acidic peroxide based oxidation reagents.

Thanks,
408

Now, either your "heterocyclic amine" substrate contains a mysterious primary amino group, which you happily protected with phtalic anhydride, or you made a really bad choice when selecting a protecting group for the endocyclic amino group.  ;)

Title: Re: Amine protecting groups
Post by: Honclbrif on December 29, 2011, 06:02:57 PM

Also, when did we go from peroxide to hypofluorous acid?

Title: Re: Amine protecting groups
Post by: 408 on February 17, 2012, 04:18:24 PM

It was a heterocyclic N-NH2 group.  Sorry for confusion.

HOF stinks. Fluorine smells like clean chlorine, but this stuff smells like F2 farted in an elevator.

Title: Re: Amine protecting groups
Post by: veselin on January 24, 2014, 11:41:37 AM

Is Phthalimide as protective group for amines stabile in alkylation with NaH/propargyl bromide? Thanks