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Nitrostyrenes to oximes with sodium dithionite

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Barium:
:o  Running in circles pulling my hair and screaming like mad

I have no idea why you got those results GC_MS. I´ve used this method on plain 1-phenyl-2-nitropropene and 1-(2,4,5-trimethoxyphenyl)-2-nitropropene too and got excellent results. I have not verified the identity of the oximes by any other method than HPLC and mp. When I have reduced 1-phenyl-2-nitropropene to the ketoxime in the past using hydrogenation, SnCl2 and CTH (sodium hypophosphite-Pd/C) the result has always been a product contaminated with about 20% P2P. The dithionite reduction gave less than 1% P2P contamination.

Was there a color change?
How alkaline did you make the post-reaction solution?

I'll get some p-MeO-benzaldehyde to see if I get the same results. Don't be surprised if there is no noticible exotherm on a 10 mmol scale. Water is a very effective heat-sink. Did you add water to the reaction by the way?

AB2: 2,5-DMNS does indeed get reduced but I fear that the oxime is, to a large extent, hydrolysed in the aqueous acidic enviroment to the aldehyde. I have no idea how the aldehyde behaves under those conditions.

Antibody2:
Barium - damn! that's really too bad. a two step circle.

I am curious an another note altogather. What is the water soluble intermediate in this reaction prior to the sodium carbonate addition?

GC_MS:
My dithionite turned out to be utter crap. It might be wise to store it in a freezer if you only use it occasionally.

Ganesha:
Good post GC_MS!

One more paper from same author on same subject:

Reduction of aldehydes and ketones by sodium dithionite

Johannes G. De Vries, Richard M. Kellogg;
J. Org. Chem.; 1980; 45(21); 4126-4129.

armageddon:
Hi bees!

I just want to know: has anyone tried the reduction described by Barium (besides GC_MS who unsuccessfully used partially decomposed dithionite?)? It seems to work so easy and nice, I wondered why nobody verified it yet!?
(I mean reduction of nitropropenes to oximes, not ketones to alcohols)

THX, A

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