[408]

Hi everyone.

I am generating a nitrile oxide as part of a synthesis path.  The solution turns green for a while.  No metals are present.  Is this normal for a nitrile oxide, or is something else occuring?

Thanks

[skyjumper]

What is the exact reaction you are preforming?

[408]

I am generating a nitrile oxide from an oxime using iodobenzene diacetate in dichloromethane.  I cannot say the exact oxime I am using.  This oxime contains no other reactive groups, but there is a nitro group nearby.  

I am getting a horrible mixture of products, not simply the desired dimerization of the nitrile oxide to the oxadiazole N-oxide, I am trying to figure out why.

[sjb]

I am generating a nitrile oxide from an oxime using iodobenzene diacetate in dichloromethane.  I cannot say the exact oxime I am using.  This oxime contains no other reactive groups, but there is a nitro group nearby.  

I am getting a horrible mixture of products, not simply the desired dimerization of the nitrile oxide to the oxadiazole N-oxide, I am trying to figure out why.

I was going to ask if the furoxan (the dimer product) was an undesired, as I know you can also trap nitrile oxides with nitriles to form 1,2,4-oxadiazoles (no N-oxide). Could it be that you're getting some form of cycloaddition with the nitro group? Have you tried other methods to generate the nitrile oxide (in the reaction I have carried out of this form I used CAN on the oxime, for instance)?

[408]

I suppose other oxidation agents are worth a try... CAN in water failed.  Perhaps I should have gone MeCN like the paper....  Not quite sure what to do on workup when the inorganic salt is so organic soluble.  I guess collumn.  If I have to.  I guess. 

I have tried to find in the lit a reaction between nitrile oxide and nitro groups, but so far no luck on that front.


But yes, the furoxan is the desired product.  Nitric oxide releasers and all that jazz.  

[sjb]

I wouldn't necessarily use acetonitrile as the solvent. At least in my case (using p-nitrobenzaldoxime), I was using acetonitrile as reactant and solvent, to form the 3-aryl-5-methyl-1,2,4-oxadiazole. I'd think that water may potentially rehydrate the nitrile oxide back to a nitro compound (isn't that another way to form the nitrile oxide, dehydration of a nitro? Is the nitro group you have attached to a tertiary carbon?)

[408]

Primary nitro group.

Indeed, nitro compounds can be used to generate nitrile oxides.  Not the reaction I am looking to try, so I am unaware of the conditions.

Thanks for the tip about water hydrating oxides to nitro.  I will bother to use dry solvents now.