I tried to synthesize a dimethylaniline from the corresponding primary amine using methyl iodide in DMF at 60 °C. The reaction gave me only one product, however this is a very polar molecule, I suspect this compound is the ammonium salt. I have used only 2.5 equivalents of the alkylating agent
Trialkylamine are more reactives than dialkylamine toward electrophile, also even you used a default of ICH3, the reaction goes in majority to quaternary ammonium. You must follow the recommandation of Manjunatha or if you would like to not lost what you have done, heat the ammonium salt, dealkylation will occured and distil out the ICH3 formed, you must recovered the tertiary amine.
You can start with halo ethane and try to add ammonia, you will get primary amine.
This primary amine when reacts with another halo ethane, you can get secondary amine. Secondary amine when reacts with another molecule of halo ethane to get tertiary amine. If you have excess ammonia in the mixture, you can get quaternary ammonium salt.
Trialkylamine are more reactives than dialkylamine toward electrophile, also even you used a default of ICH3, the reaction goes in majority to quaternary ammonium. You must follow the recommandation of Manjunatha or if you would like to not lost what you have done, heat the ammonium salt, dealkylation will occured and distil out the ICH3 formed, you must recovered the tertiary amine.
Dear Ruben,
You might want to try reacting your quaternary ammonium salt with lithium aluminum hydride. This should produce methane and your desired tertiary amine.
Sincerely, Howard
Thanks a lot for all wonderful and brilliant answers... I will try the Eschweiler–Clarke reaction in a new experiment
I may be misreading your question. However, if I am understanding in that you have 'over-alkylated' an amine to it's quaternary ammonium salt and want to 'dealkylate' it to the respective tertiary amine, there are ways.
The selective demethylation of quaternary ammonium salts. Maurice Shamma, Norman C. Deno, Joseph F. Remar. Tetrahedron Letters. Volume 7, Issue 13, 1966, Pages 1375–1379
A method for the demethylation of N+-methyl quaternary ammonium salts. N.D.V. Wilson, J.A. Joule. Tetrahedron Volume 24, Issue 16, 1968, Pages 5493–5497. http://dx.doi.org/10.1016/0040-4020(68)88147-5
I'm sure there are others as well, this was a cursory literature search.
There are even 'conveniant' ways to go from the tertiary to the secondary. Again as other people have suggested there are more selective means to alkylate amines. Other methods for alkylation 'control' off the top of my head are huenigs base, and DMSO + K2CO3, as well as sillica gel and TEA if I recall correctly. Unfortunately almost all of those fail for methyl.
An interesting, cheap and facile twist for reductive alkylation that may work for your substrate is:
Reductive methylation of primary and secondary amines and
amino acids by aqueous formaldehyde and zinc.Renato A. da Silva,a Idalia H. S. Estevamb and Lothar W. Biebera.Tetrahedron Letters 48 (2007) 7680–7682.
If the problem is work-up related however, you can likely run your product through a plug of sillica gel. Works for most quat. amines.
alkylation of amine gives quaternary ammonium salt .which on pyrolysis convert into tertiary amine
- Badges
- Science method
- Similar topics
- Chemistry, Organic
- Synthesis