marksev1
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Selective protection of aliphatic amine in the presence of an aromatic amine
Hello everyone!
I'm looking for a protective group for a more or less selective protection of an aliphatic primary amine in the presence of an aromatic primary amine.
Obviously an aliphatic amine is much more nucleophiic that an aromatic, I am aware of that, and a possible eletrophile would be attacked by the more
nucleophilic one.
The drawback is i can't use strong acidic or basic conditions for removal of the protective group (I have a methyl ester also in my compound. I'm
looking towards phtalimide (and later deprotection with hydrazine, heard that its quite hard to later get ride of the side-product of the removal of
the protective group). Any hints about that?
Could you also suggest any other protective group and maybe conditions, would maybe some carbamate work?. Sorry that I am asking to be spoon fed but
at the moment i don't have access to Scifinder, some problems with Windows Vista.
There's also a phenol -OH group on the compound which could compete in the reactions of protecting the amine. And sorry i can't draw the compound.
On Google I've found a reference for a selective protection of an aromatic amine in the presence of an aliphatic but that doesnt help me obviously.
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Nicodem
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Obviously, nobody can help you if you don't provide enough information about the reaction for which you need to protect the aliphatic amine. Certainly
the easiest way to protect the aliphatic amine and direct electrophiles toward the aniline function is to monoprotonate your compound. The difference
in basicity between aliphatic amines and anilines is about 10000-times, thus a monoprotonation provides an excellent protection. But unless you give
more details it is impossible to provide the details on how to do this and if applicable at all.
Otherwise, Cbz protection is fine if you want the deprotection to be performed in neutral media (via hydrogenation). Boc can also be deprotected in
neutral media by thermolysis at 200-220°C, but if the ester group is the only reason to avoid acidic conditions you can also remove Boc protection
with CF3COOH/CH2Cl2 which tolerates methyl esters (though you'll might have to use HCl/MeOH instead if the aniline trifluoroacetate is insoluble in
CH2Cl2). Fmoc protection should also be applicable as piperidine used in deprotection reacts with methyl esters only very slowly. But then again some
of these protecting groups might not be suitable for the reaction you want to perform.
Try installing another version of the Citrix client if you have troubles with SciFinder under Vista.
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unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
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