Author Topic: 2,4,5-triMeOP-2-P oxime  (Read 793 times)

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Barium

  • Guest
2,4,5-triMeOP-2-P oxime
« on: June 11, 2002, 06:40:00 PM »
25,3 g (100mmol) 1-(2,4,5-trimethoxyphenyl)-2-nitropropene was suspended in 1000ml IPA or EtOH and 800mg 5%Pd/C was wetted with IPA and added to the suspension. 39g (370mmol) sodium hypophosphite monohydrate was dissolved in 50ml warm water and added in portions to the nitroalkene suspension under violent stirring. The exotherm will easily bring this to a boil, but keep it at 40-50 deg C by immersion in a cold water bath. The reaction is finished when the top alcohol layer is colorless or has just a very slight yellow color left, this takes roughly two hours. Celite was added (three or so teaspoons) and the mixture is stirred for a minute and then filtered at the water pump. The filtrate quickly separates in two layers. The bottom aqueous layer was removed and the top layer was transferred to a rotovap, and the alcohol removed by distillation. This leaves a oil which quickly forms crystals which can either be dissolved in some DCM or toulene, filtered from a small amount of salts and stripped of solvent to give quite pure (98%) oxime and then further reduced to the amine (TMA-2), or the crude oxime can be hydrolysed to the ketone by acid hydrolysis.

Yield 23,4g (98%) 1-(2,4,5-trimethoxyphenyl)-2-propanone oxime

I have performed this reaction for about 6 months now. In the beginning I only got some 70% yield. But now, without having really changed anything, I get 97-98% everytime. Wierd! But I like it.. :P

Rhodium

  • Guest
You keep impressing us
« Reply #1 on: June 11, 2002, 07:45:00 PM »
Great! Do you have any references for this reduction, or is it your own invetion?

Barium

  • Guest
Edit time..
« Reply #2 on: June 12, 2002, 09:13:00 AM »
It should say...100ml EtOH or IPA not 1000ml.

Rhodium. Thank you.. :)  I´ve read alot about CTH using hypophosphite donors. After trying a few of the published methods I started to modify them a bit, like less catalysts loading, diffrent solvents and so on. The result is this nice method.

This method does, so far, not work with nitroethenes .


Barium

  • Guest
EtOAC as solvent
« Reply #3 on: June 12, 2002, 09:49:00 AM »
EtOAc can also be used as solvent in the CTH. This gives better yields of oximes which are sensitive towards hydrolysis. Such a reaction would look like this:

Nitropropene 100mmol
Sodium hypophosphite 300-400mmol (watch the color change)
5%Pd/C 2-3% w/w to the substrate
EtOAC 50-60ml/25g substrate
Water (warm) 1,5x the weight of sodium hypophosphite (15ml to 10g hypophosphite).
IPA or EtOH as PTC, just a couple of mls.

If substrate, catalyst, aqueous hypophosphite, EtOAc is combined in a flask nothing much happens until 4-5ml IPA or EtOH is added. A nice way to avoid ignition of the solvent is to add the catalyst first to the reaction flask, then the dry substrate. Make sure the substrate really covers the catalyst. Then add the EtOAc followed by the alcohol, and finally aq. hypophosphite in portions.