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Topic: CH3 of toluene to NH2  (Read 18167 times)

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Darkstar

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CH3 of toluene to NH2
« on: September 22, 2004, 03:06:51 PM »
How do you replace the methyl group of toluene with something else (specifically NH2). It's so stable I can't remember a method to tear it off.


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Re:CH3 of toluene to NH2
« Reply #1 on: September 22, 2004, 04:57:55 PM »
Are you trying to make aniline or benzyl amine?

For benzyl amine you could oxidize with KMnO4 to give benzoic acid, then make the amide with ammonia, then reduce to benzyl amine with LiAlH4.

I'm not so sure about making aniline from toluene though.  You might be able to oxidize to benzoic acid with KMnO4, then make the acid chloride with SOCl2, then add sodium azide and heat the crap out of it to do a Curtius rearrangement.  That'd probably work.  There might be a more direct method though.

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Re:CH3 of toluene to NH2
« Reply #2 on: September 23, 2004, 03:42:50 AM »
Both, Curtius and Hoffman rearrangements work in this case with yields of 60-80 %
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Re:CH3 of toluene to NH2
« Reply #3 on: September 23, 2004, 06:45:18 AM »
Yes, I mean aniline. If Curtius and Hoffmann do work with arenes, that's good.

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Re:CH3 of toluene to NH2
« Reply #4 on: September 23, 2004, 11:46:06 PM »
I do not see how you could take that methyl off toluene ???
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Re:CH3 of toluene to NH2
« Reply #5 on: September 27, 2004, 01:21:40 PM »
Well, once you have the azidoamide of benzoic acid you do the Curtius rearrangement.  In the mechanism you lose a molecule of nitrogen and get a nitrene (like a carbene, but with N).  Then the aryl group migrates and you can push the electrons to make an isocyanate intermediate (so, Ar-N=C=O).  The isocyanate is then hydrolyzed upon work-up and you lose the carbon from the methyl group of the toluene as CO2.

You can also draw a polar mechanism where the aryl group migrates and displaces molecular nitrogen, but I like the nitrene mechanism better.

BTW, this is almost exactly like an Arndt-Eistert homologation, but with nitrogen instead of carbon.

anhuiw

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Re:CH3 of toluene to NH2
« Reply #6 on: October 01, 2004, 10:44:20 PM »
CH3---COOH----CONH2-----NH2

« Last Edit: October 01, 2004, 10:46:48 PM by anhuiw »

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