Boffis
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N-Dimethylation of aromatic nitro-amines
I have been wondering if it is possible to prepare nitro-dimethylanilines by the N-methylation of the appropriate nitroaniline.
Magpie had a thread on the methylation of aniline with methanol under pressure but I am not sure that the nitro groups would withstand this sort of
treatment. Does anyone have any experience of such methylations using the more usual reagents such as methyl iodide or dimethyl sulphate etc.?
It may be possible to arrive at the 2 and 4-nitro-dimethylanilines by condensing the appropriate nitro-halobenzene with dimethylamine. This is
certainly possible from 2,4-dinitrochlorobenzene. But 3-nitrodimethylaniline is not going to be accessible via this route and this is one of my
primary targets.
There are procedures in Weygand & Hilgetag's book Preparative Organic Chemistry in the forum for o-bromoaniline. However, in an unreferenced,
almost throw away comment, they state "provided the amine is sufficiently basic". The problem I see it that nitroanilines are much less basic than
aniline. I don't know how o-bromoaniline compares but the yield is given as only 54%.
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Lionel Spanner
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The Eschweiler-Clarke reaction (formaldehyde and formic acid) is a typical method for making tertiary methylamines, and unlike methyl iodide it
terminates cleanly at the tertiary amine.
Not sure how well it'd work on nitroanilines though.
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clearly_not_atara
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Nitration of aniline goes to para, then meta, due to electrostatic repulsion. Nitration of 4-bromodimethylaniline should go almost exclusively to
meta, and then the bromine should not be too hard to remove, hopefully?
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