Dean Stark trap with nitropropene/styrene prep.

[Bandil]

Some time ago, swim enquired about the preparation of relative pure 2,5-dimethoxy-betanitropropene. I believe Rhodium suggested the use of a dean stark trap, if the nitroethane was not 100% anhydrous. According to the original preparation of the nitropropene:

A solution of 10.0 g 2,5-dimethoxybenzaldehyde in 50 mL glacial acetic acid was treated with 6.8 g of nitroethane and 4.0 g of anhydrous ammonium acetate.


AFAIK a Dean stark trap works by separating the water that is distilled azetropically with the solvent. But, in this case the water is soluble in the solvent acetic acid. How could a DS trap be used here? Even with nitroethane as the solvent, it could not work, as the nitroethane has a weigth of 1.05 g/mL and would thus form the lower layer...

Any ideas on how to get this scheme to work?

regards
Bandil

[Xicori]

it should work to just substitute the GAA with Toluene or Benzene - but i´m not completely sure on that, but it works with P2NP...


lg
xicori

[Bandil]

Do you have any refernces on that reaction?

[Antoncho]

There's a proc on Rh's for o-methoxy-P2P.

Also TFSE will give you Barium's excellent proc for hard-to-make nitropropenes and nitrobutenes.


Antoncho

[Rhodium]

I suggested the use of 0.1 equiv. ethylenediamine diacetate in IPA at RT for 24h, gives 50% yield of pure nitropropene, the same yield as the ammonium acetate procedure in Pihkal but with less work. Directions can be found in edda.html at my page.

[hest]

Use benzene as solven and KF/ethylenediamine diacetate /Am.Formiat/cyclohexylamin/ect. as the catalyst then let the DeanStarc work 24houers.
Byt the synt of 2,5-dimetho... in a mw. works so nice, why bother onyething else. For some off the other aldehydes it's a different history.