reduction of an amine-oxide
Hello,
Please correct me if I placed this post in the wrong section.
I'm planning on doing a reduction of an N-oxide, the oxide of a tertiary amine, to the corrosponding amine. My N-oxide is pretty hydrofilic, so water,
methanol or ethanol sound good as solvent.
I'm in doubt between two routes; sodium borohydride and zinc/acetic acid, but I can't seem to find much references on reduction of aliphatic N-oxides
specificly, but from what I understand the oxide is reduced pretty easily and aliphatic N-oxides are more readily reduced than the aromatic.
This is one of the references I found, they use Fe instead of Zn but that should be exchangable;
http://syntheticfocus.com/general-procedures/other/reduction...
Some general information about amine-oxides:
http://www.scribd.com/doc/30132815/Amine-Oxides
My amine-oxide has two beta hydrogens so the Meisenheimer rearrangment isn't possible, although the Cope ellimination is still possible so high
temperatures are to be avoided.
In section 3.2 they say aliphatic amine-oxides are readily reduced by sulfurous acid at room temperature, but I don't like working with SO2 since I
don't have a fumehood. But they also say they are readily reduced by zinc in acid.
So with respect to both references I came up with a protocol of myself:
1mmol of N-oxide is dissolved in 20ml of water and 1ml of acetic acid and placed in a ice-bath. To this 5mmol of zinc powder was added and the
reaction was monitored bij TLC. If no reaction is seen after a couple of hours the temperature can be put up. If this doesn't work I could try a
higher amount of AcOH.
For the sodium borohydride reduction I can't find any references. But I could do small scale test, by dissolving the N-oxide in methanol and adding
5-10 equiv. of NaBH4 and following the reaction by TLC.
Do these reductions sound plausible to you? Or does anybody have a reference for me?
Edit: Sodium dithionite reduction seems feasable aswell, in luminol synthesis it is used to reduce a aromatic nitro group to the amine, in 3M NaOH.
Does anyone has comments on this?
http://ochemonline.pbworks.com/f/09_luminol.pdf
[Edited on 5-6-2011 by Tsjerk]
[Edited on 5-6-2011 by Tsjerk]
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