[rolnor]

I am working with N-oxides in a cyclic molecule, I have looked in my textbooks but I can not find any mention of chirality in N-oxides in the way it is for sulphoxides for example.
Is it possible to get chiral amineoxides?

[AWK]

In quinine - nitrogen atom in quinuclidine group is chiral, even without N-oxide function (impossible inversion at nitrogen).

[rolnor]

Yes, I know that you can have amines in ringsystems chiral, but I mean if inversion is possible? As example whe have sulphoxides?

[lb2]

Any amine oxide in which the three R groups attached to N are different is by definition chiral. But maybe what you really mean instead of "chiral" is more something like "enantiopure"?

In contrast to the sulfur atom in sulfoxides, the nitrogen in amine oxides does not have a free lone pair. So while sulfoxides could invert and be stereochemically unstable because they have a lone pair, that inversion is slow so they are generally stereochemically stable. In contrast, inversion is not possible with amine oxides (why do you think?) So if you can obtain one enantiomer of an amine oxide, it will be stereochemically stable. You should be able to find several examples of chiral amine oxides (for example, several proline N-oxide derivatives have been tested in catalysis.) They're just not used all that much, except for pyridine N-oxides, because they tend to be not so stable, especially on heating.

[rolnor]

My initial thought was that it should be chiral but in my Marchs Adv. org. chem it is not mentioned at all, I have seen one such proline derivative though. I have made one N-oxide with twoo stereocenters including the N-oxide nitrogen and it looks on TLC that they separate but on NMR they are identical. It thus seem as if I get only oxidation on side, probably the less hindered and ends upp with only one isomere. I will post the structure so you can judge for yourself.
Thank you for the answer.

[rolnor]

Here is my N-oxide. The six-membered ring makes it more stable because it can not eliminate with the Cope-elimination type reaction off course. If it was racemic on both nitrogen and carbon I should get diastereomeres and they should give different NMR-spectra so I think it might be the m-CPBA attacks from the least hindered side of the amino-group or what do you think? The carbon is racemic in this test compound but I will do the pure enantiomere later on.

[critzz]

You'd indeed expect stereo-selective oxidation of the amine, but I find it hard to believe that its (close to) 100%.
Especially since there is no apparent mechanic (like a Fürst-Plattner diaxial attack) involved. Are you positive that there
is no possible overlap of peaks in your NMR-spectrum?
To be sure you could run a LC-MS if available.

[rolnor]

Me too expected a mixture and it looked as if I got separation on silica flash-chromatography but the twoo fractions have identical carbon and proton NMR. I dont have LC-MS but I will run HPLC och nano-TLC. I am thinking of running single crystal XRD if I can get a nice crystal, but I dont have much experience sadly of this tecnique, NOE-NMR could also perhaps show wich isomere i got.