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Nitrostyrenes to oximes with sodium dithionite

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Barium:
This is the easiest way so far to reduce nitrostyrenes to oximes. I haven't been able to get all the way to amines yet, but that's just a matter of time. I know I'll be able to get amines with this lovely and cheap as shit reducing agent. The best route to amines is probably reduction to nitroalkanes with aqueous sodium borohydride/PTC followed by dithionite-reduction to the amine.


General procedure for reducing nitrostyrenes to oximes

100 mmol 1-(2,4-dimethoxyphenyl)-2-nitropropene (22,3g)
250 mmol Sodium dithionite (43,5g)
MeOH, EtOH, or IPA
Water
Sodium carbonate

To a 500 ml roundbottom flask equipped with a magnetic stirbar is added the nitrostyrene and 25 ml MeOH and stirring is started. Sodium dithionite is added in one portion followed by 100 ml water. Immediately when the water is added the yellow color of the alcoholic solution dissapears. The temperature remains steady for about five minutes when suddenly almost all of the nitrostyrene dissolves and gets reduced within one minute and the temperature increases to about 60°C. The mixture is now completely colorless. Stirring is continued for five minutes while cooling is applied by surrounding the reaction vessel with cold water.

When the temperature has dropped to 20°C solid sodium carbonate is added in portions to neutralize the acidic solution. When the pH 8 has been reached 200 ml cold water is added to the flask. When more sodium carbonate is added and the pH increases to above 10 the colorless solution turns cloudy and a crystalline mass falls out. The addition of sodium carbonate is continued until no more crystals forms. The mixture which is now very thick with white crystals is filtered and the crystals are washed once with 5% acetic acid and twice with cold water.

Yield 18,1 g 2,4-dimethoxyphenylacetone oxime (87%)

moo:
Why don't you go drink a few pints with Varma and Kabalka and brag a little about your research! ;)  Good work!

Chimimanie:
Yes, I knew we could use good ol' dithionite for our purpose....

That is great to have researchers like you, Barium, to test new routes.

8)

Antibody2:
love oximes, awesome work barium. wondering how this might fare on nitropropenes?

SpicyBrown:
Does anybody know if the aldoxime resulting from this type of a procedure on a phenyl-2-nitroethene would stand up to reduction by sodium metal in ethanol?

-SpicyBrown

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