I am trying to functionalize a polymer, containing tertiay amine pendant groups, which is supposed to convert into quaternay ammonium cation after reacting with epoxide. I had tried the reaction under acidic conditions (using TFA) in DCM, but so far it's not working. I am now trying with basic conditions (triethylamine), let's see if it works. Anyone already tried this kind of reaction, any help/insight would be appreciated in this regard!
Thank you!!
Hello Sidra-
Nucleophilicity of that amine will depend on the type of substituent groups. In any case, TFA is just an acid that will open the epoxide but I can't believe it will be available to react with your amine.
One option that could help you is just to add an excess of epoxide with respect to the polymer using DMF as a solvent, heating and stirring overnight (mechanical stirring). This a procedure that I have used and it works good.
Hoping my answer be of help of you,
BR,
Julián de la Hoz-
I don't think this works very well. Tertiary amines are often used as catalysts in the ring opening of epoxy rings but do not ring open the epoxy very well themselves. Tertiary amines like triethylamine are more sterically demanding than you might think!
In this reference they use polymers with epoxy end groups, they ring open with a tertiary amine containing thiol, then quaternize in a separate step:
http://polymer.chem.cmu.edu/~kmatweb/2000/November_00/Polym%2CBull/destais.pdf
When we made quaternary ammonium photobase generators, (Article Synthesis and Photochemistry of Tertiary Amine Photobase Generators
) we found this as well - for benzhydryl amine, we were able to exhaustively methylate (quaternize with methyl groups) but not with any other alkyl groups - so you could add 2 ethyls but not a third. The benzhydryl chloride also would not react with tertiary amines to quaternize. The fluorenyl chloride or bromide could react - but the best quaternization is with DABCO and quinuclidine where the alkyl groups are kept back.But this is old news: J. Am. Chem. Soc. 1949, 71, 2, 445–450
So a polymer with pendant tertiary amines is a limited starting point. Your best bet for alkylation is iodomethane. If you want the quaternized ammonium and the OH from the epoxy better to start with the epoxy as the pendant group.
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