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stoichiometric_steve
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80% molar yield after distillation of the base from the 150mmol batch (see writeup above). very cool  best workup ever!
85% molar yield after distillation from a 268mmol batch, using 15% w/w 10% Pd/C catalyst.
take my word: keep water out of the workup until you get to the a/b purification, and you will be a happy chemist.
[Edited on 21-9-2007 by stoichiometric_steve]
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DNA
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After a lot of trial and error I finally decided to give Pd/C a try.
I tried to reduce some 3,4,5-trimethoxynitrostyrene with BF3.Et2O/NaBH4 (2,5-dimethoxynitrostyrene worked like a charm though) and with Al/Hg and
LiAlH4 and none of them gave me succes.
So well Pd/C then now, I read the article that was posted that uses HCOOH and Et3N that is also what I hear from experienced organic chemists that
that is a good way to go.
Now I was wondering has anyone already tried the HCOOH/Et3N method?
Has anyone used this substrate already?
And at what temperature does the nitroalkene boil, since I do have a vacuumpump but it is one like this:
http://www.dialab.hu/dat_vakuumpumpak/vakuumpumpa_nagy.jpg
A double waterjet pump, which draws vacuum up to 8mbar at 2°C and 20mbar at room temperature.
I don´t know if that´s good enough?
Thanks in advance.
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stoichiometric_steve
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| Quote: | Originally posted by DNA
And at what temperature does the nitroalkene boil |
3,4,5-trimethoxy-beta-nitrostyrene cant be distilled with your pump, and i bet that neither can the corresponding nitroalkane. you need a rotary vane
oil pump pulling at least 2-4mbar (and all the other things that you need for using such a setup, i.e. vac gauge, controller or needle valve, cold
trap).
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DNA
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Ow okay well doesn't really matter I'll use other methods to purify it then.
But haven't you tried the HCOOH method yet with Et3N?
And I've got Pd/C 10% oxidated form, and I read some things about PdO/C reduction does it really matter if it is Pd of PdO on carbon.
And when they say 10% by weight concerning the patent do they mean already with the water or just Pd/C so like 10g substrate there you need 1g Pd/C
does that mean 500mg Pd/C with 500mg water or 1000mg Pd/C and 1000mg water.
And I do have a manometer which goes up to 0mbar so I do have the vac gauge or is that not what you ment?
Thanks for the quick reply by the way.
DNA.
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stoichiometric_steve
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| Quote: | Originally posted by DNA
But haven't you tried the HCOOH method yet with Et3N?
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no.
i have no idea if your catalyst is suitable. drop a bit of it into HCOOH and if there is gas evolution, it's good.
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DNA
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Just one more thing since it saves like 50% of your precious catalyst.
When it says 10% by weight concerning the patent do they mean already with the water or just Pd/C so like 10g substrate there you need 1g Pd/C does
that mean 500mg Pd/C with 500mg water or 1000mg Pd/C and 1000mg water.
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stoichiometric_steve
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| Quote: | Originally posted by DNA
Just one more thing since it saves like 50% of your precious catalyst. |
sigh...they say that in the patent, catalyst weight refers to 50% wet catalyst.
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DNA
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Sorry for that stupid question, maybe something interesting here.
Although the pictures aren't working anymore:
http://www.erowid.org/archive/rhodium/chemistry/345-meo-ns.h...
Here is stated that the nitroethane crystalizes out so no need to distill this compound as it can be purified in other ways as mentioned before about
solid compounds.
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transformer
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Pictures where sent to fire from erowid but not updated... here is the version with pictures:
http://psychedelichosting.info/Ionium/Rhodium/chemistry/345-...
Good luck!
[Edited on 26-9-2007 by samsung]
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DNA
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Reduction was a succes but got 2,380g nitroethane out of 4,78g of nitrostyrene.
Only used EtOH and too much glacial acetic acid.
Nice white crystals after recrystalization out of methanol.
samsung thank you very much for posting this link!!
Read a lot of your posts.
DNA
[Edited on 3-10-2007 by DNA]
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DNA
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PdO/C should work an experienced organic chemist told me but it didn't work for me.
So now I got 5% Pt/C, anyone knows if you need less of that compared to Pd or what the advantages or disadvantages are...
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Klute
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Bringing this old thread back to date....
A CTH was tried on 2-MeOphenylnitroethane, obtained by NaBH4 reduction of 2-MeOnitrostyrene (4eq, in EtOAc/EtOH solvant system), giving a medium
yeild, and a strange, neutral compound......
The nitrethane was obtained as a yellow oil, out of which some white solids precipitated after a day in the freezer, under Argon, and the oil was
opaque even when warmed back to RT. The whole appearance bothered me. TLC indicated a minor impurity, thought to be the dimer.
So the oil was purified by a quick coluum chromatography. Being out of solvants, and not finding a terribly efficent system, 50:50 acetone/pet.
ether was used, more concerned of using the cheapest solvants than the most suitable, eevn though thats system offered a cceptable seperation of the
two spots and a rather rapid elution.
After evaporation of the eluant, a nice, limpid pale yellow oil was obtained. Unfortuanly, the second stain was still present, even though there
wasn't anymore of those inorganic salts left. Teaches me right to be such a lazy-ass and not redistill my recylced DCM.
(I haven't got my notes at hand, so don't recall the amount used, this was a little time ago, so here is only a brief describtion of the CTH)
The oil was then added to a 100mL 3 neck, containing 5% w/w to substarte of fresh 10% Pd/C, covered with IPA. More IPA was added.
No here is something strange. As more IPA was added, the whole suspension became more and more milky, to a point where it gave a clear, slightyl
milky greenish/yellow solution, but the Pd/C agglomerated into small particules. This made me doubt the IPA was anhydrous, possibly the 91% azeotrope
(it is supposed to be technical dry IPA, purchased from an industrial supplier).
10mL of the same IPA was added in a test tube, and some NaOH added. It clumped up a little, the IPA turned a little milky, but no aq. layer was to
be seen. I believe this a test of dry IPA. I will try mixing it with 8vol of pet. ether. So if this was indeed 91% IPA, the large ratio of water could
explain the mixed results of the CTH.
I should have used ETOH or MeOH, as I did before. I'm much more confident of the purity of these two.
5eq of HCOOK (80% HCOOH on slurried KOH à la Barium) was then added dropwise. GAs evolution started quickly, and the Pd/C gradually turned back
to a fine suspension. This was heated to 50-60°c over 2 hours. 2eq of 80% HCCOH was then added very slowly dropwise. The flask was left at reflux for
another 4H, and left to cool down for 10H.
The black suspension was then neutralized with AcOH, the catalyst filtered, the IPA removed under vacuum until temp increased, the aq. washed
several times with DCM (the first wash came out yellow, much darker than previous CTH on different substartes), gently basified with 10% NaOH,
extarcted with DCM, the extarcts washed with brine, dried, and the DCM removed to leave roughly 50% yeild of the amine. Not very satisfying.
Now, the first DCM washes of the acidfied filtrate were simply left in an erlenlmeyer, on a shelf for a rather long period. When cleaning up a few
days ago , I realized the DCM had evaporated, and that a rather large yellow crystalline mass remained in the erlenmeyer. A pretty large amount
compared to the amount of substarte used.
What is this compound???! The nitroethane is an oil at RT, so it can't be it.
Could it be that the CTH, with a much larger amount of water than needed, yeild a different compound? Improbable. I recall Stoechiometric_Steve
using 70% aq. MeOh with amm. formate. this could be the cause of the bad yeild though.
What I though was that the NaBH4 reduction possibly wasn't as effective as it seemed, and that the TLC spot was actually unreacted nitroalkene, and
this nitroalkene yeiled a ketoxime or something similar during the CTH. But these NaBH4 reductions usually proceed very well, especially with 4eq of
hydride. And the stain would have been much larger. Unfortuanly, i think I have thrown away most of the plates, and I'm not sure if I've kept a sample
of the crude nitroethane, to compare with the nitroalkene. I'm pretty sure I must have compared the first TLC with pur nitroalkene though, I always
do.
Another idea that popped up: could heating the nitroalkane with acetone (when removing the elution solvants) cause some kind of condensations?
Maybe I damadged half of the nitroalkane before the reduction, and that was the starnge stain that remained after the coluum..... God knows what that
could have given after 10H CTH reduction....
ANy ideas as what this could be? If it's an oxime, it would hydrolyse pretty easily, no? I can't acces NMR in near futur, not for home experiments
anyway, and can only use liquid films IR for the moment. Any help/advice would be appreciated!
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DNA
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Dear klute,
I've been busy on this subject A LOT lately.
About the nitroalkene it runs completely to the top with pure ethylacetate and also with DCM/MeOH (98% DCM, 2% MeOH) on TLC. See if that yellow
crystals do this or stay at the start, that's already a conclusion if it are salts or an organic compound.
Look at solubility in water and in MeOH, for the furtherrest try to make an IR of it.
And something interesting for everyone SWIM tried Pd/C with HCOOH and Et3N.
It works like a charm, it gives really great yields. And if anyone is looking for the paper where a lot of people are refering to when doing NaBH4
reductions I can upload it if there is interest for it.
This is the one.
Sodium borohydride reduction of nitrostyrenes by Reverse addition: A simple and efficient method for the large-scale preparation of
phenylnitroethanes.
Synthesis, 1985, 9, 886-887
... has been fucking around with reducing nitrostyrenes to nitroethanes and also got moderate yields, but now when using this paper, yields are great
.
And ANOTHER interesting thing, reducing nitrostyrenes directly to the amine with Fe/HCl.
Also got the paper about that one, also worked but in like 65-70% yield.
[Edited on 3/3/2008 by Nicodem]
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stoichiometric_steve
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| Quote: | Originally posted by DNA
Sodium borohydride reduction of nitrostyrenes by Reverse addition: A simple and efficient method for the large-scale preparation of
phenylnitroethanes.
Synthesis, 1985, 9, 886-887
SWIM has been fucking around with reducing nitrostyrenes to nitroethanes and also got moderate yields, but now when using this paper, yields are great
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if you consider that Dioxane is not quite the solvent of choice regarding toxicity and other safety aspects, this procedure is not as attractive as
you would probably like it to be. it is a pain in the ass to recover and an environmental hazard...
would you please tell us which nitrostyrene you reduced via Fe/HCl and in what yields?
Klute: you probably had some unreduced nitrostyrene and/or nitronate in your CTH mix. if you get a color change (blue, greenish) upon addition of the
catalyst, there's something wrong. i got this once, too - and the yields were insignificantly low.
cheers,
steve.
[Edited on 3-3-2008 by stoichiometric_steve]
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DNA
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... used 3,4,5-trimethoxynitrostyrene which he reduced to the corresponding amine with Fe/HCl.
Dioxane is not that hard to recover actually, with a rotary evaporator and a vacuumpump it comes off quite easily.
And besides the reaction mixture is extracted with dichloromethane, and then the dioxane is not a problem anymore.
Edit by Nicodem: No SWIM-ing on this forum!
<sub>next time you do that, I'll remove the entire post</sub>
Sorry didn't know it wasn't allowed.
[Edited on 3/3/2008 by Nicodem]
[Edited on 3-3-2008 by DNA]
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Klute
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DNA, DCM works very nice as an eluant with 3,4,5-MeO substarte, for both the alkane and alkene. Otherwise, 5-10% DCM in pet ether is my favourite
choice of eluants.
The crystal are definatively organic. Not comparable to the nitrostyrene or nitroethane. I'm in favor of the ketoxime. Maybe this particluiar
substarte needs longer reaction time with the NaBH4 reduction.
Using EtOAc/EtOH solvant system alwayys works like a charm for me, though the crude product needs purifying for best CTH results. When the
nitroethane is solid, it's best to recyrstalize it.
A short coluum for oil would be more than enough, but with a correct solvant system. Also, using home-made silica gel is less than ideal, as it
displays a very slow flow afetr grinding in a pestle and mortar (not talking of the noxious fine silica dust, a specific dust mask was used while the
silica was dry). Maybe grinding it when humid with solvant could help getting suitable mesh size, as seiving the dust isn't really an option.
I will try hydrolysing the compound and see what comes out.
DNA, would you care to elaborate on the TEA/Formic method? I guess you followed the "New trends..." paper mentionned earlier in the thread?
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DNA
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Well about the Et3N/HCOOH method.
As long as you have no other things on your molecule besides the nitro that can be reduced, or well let me put it like this the method works great but
if you have a functional group which you want to keep intact like a carbonyl then do not use this because it is really a violent reducing agent it
especially if you use the method described in the top of the paper about exothermic and small amount.
Anyway since most of the time only thing you have is a nitro or a double bond and a nitro this works great, you don't have as stated the
ammoniumformate in the condenser and only CO2 will come off and H2. I still need to try this on the nitrostyrene to see if it reduces the double bond.
Before I did try to reduce nitrostyrene to the amine but it took 48u of hydrogen bubbling threw Pd/C (10%) 10% by weight.
So 1g substrate and 100mg Pd/C(10%) and then 48u bubling H2 will also yield the amine (monitored by TLC).
Probably this will go a lot quicker with Pd/C and Et3N and HCOOH but as I sayd before, I still need to try this.
And I also tried once to freeze the whole mixture of the reduction of nitrostyrene to the nitroalkane. This will give nice white powder but contains
also the salts, but well yeah now I use the dioxane/EtOH method and works also fine.
How do you extract the nitroalkane?
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Klute
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The nitroalkanes was simply obtained after acidification, addition of brine, seperation, brine washes and drying of the organic, followed evaporation
of the solvant.
Indeed, you seem to have been busy!
So you have manadged to obtain the amine by catalytic hydrogenation of the nitroalkene with 10% Pd/C? Are you totally
sure this is the amine? IIRC, only oximes could be obtained by cat. hydrogeantion, without using ridiculously high amount of catalyst or excessive
pressures. Was the hydrogenation performed at atmospheric pressure?
With the TEA/HCOOH CTH, how did you insure yourself that you got rid of all the TEA? Multiple aq. washes? Did you distill your freebase?
I recall a method of reducing nitroalkene to nitroalkanes with TEA/HCOOH "azeotrope" in DMF, without any catalysts.
If a different solvant could be used, a one pot reduction could be possible, although I'm pretty sure the method relies on the high bp of DMF to
give off CO2 and reduce the double bond. I'm not sure DMF would be adequate for CTH conditions.
In a perfect world were ideal conditions could be found for both reductions, the double bond could be reduced with TEA/HCOOH, then Pd/C added and
the nitro reduced by conventional CTH. Just an optimistic idea though. If I ever were to try such a reduction (the double bond reduction), of which
I've never heard of anyone trying BTW, I would obviously isolate the nitroalkane to determine yeild/purity.
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DNA
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The Pd/C;Et3N;HCOOH reduction is so vigorous that it will reduce double bonds at atmospheric pressure it makes hydrogen in situ.
Also the reduction with Pd/C in ethanol and bubbling H2 threw it was at atmoshperic pressure.
I distilled the amine to get rid of the triethylamine, adding some toluene might also carry the Et3N with it since the boiling point of the Et3N isn't
that high compared to the actual amine that is the product.
LC-MS and NMR showed that products were clean.
I found it takes a lot of solvents to extract/dissolve the nitroalkane that's why I was wondering.
Often I find solids in the seperatory funnel...
[Edited on 3-3-2008 by DNA]
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Klute
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Well, the intial aq. layer was extracted with another 3 portions of AtOAC obviously. I've never noticed the nitroalkanes been specialy difficult to
dissolve. When recrysatllizing solid nitroethane, very little MeOH is needed...
That atmospheric catalytic hydrogenation really intrigues me. So you stirred the substarte in EtOH for 48hours under H2 atmosphere, no added HCl?
What where your yeilds? Again, i remember alot of people trying this out some years ago and never getting decent yeilds of amine... I guess this is
the kind of reaction I really need to see with my own eyes....
Please lets us know about the TEA CTH on the nitroalkenes. Again, most of the litterature claims oximes are obtained by CTH on nitroalkenes. This
would be quite an improval.
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DNA
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I will do more experiments and provide you guys with an LC-MS measurments during the reaction, like after 1 hour and 3 hours and 8 hours etc. Both the
Pd/C with H2 bubbling and also the Et3N/HCOOH/Pd/C method.
And yes the 48h reaction was indeed under atmospheric pressure just bubbling the H2 threw there.
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stoichiometric_steve
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| Quote: | Originally posted by DNA
And yes the 48h reaction was indeed under atmospheric pressure just bubbling the H2 threw there. |
that sounds peculiar.
as far as i know, there are no such references in the literature.
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Klute
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There are a few articles, being worth what there are, dealing with this, but they often use a equal weight of catalyst to substrate! That hardly is a
catalyst anymore...
From the Rhodium Archive:
Synthesis of Phenethylamines by Catalytic Hydrogenation of Nitrostyrenes
Bull. Chem. Soc. Jpn. , 63(4), 1252-1254 (1990)
But again, all previous work from different forum mebers lead to think only the oximes where attainable. IIRC, a 2 step hydrogenation
nitroalkene-->oxime--> amine was possible, but the catalyst had to be changed, and I even think that was with pressurized hydrogen.
Solo, if you are reading this, wasn't it you that tried that out?
So if the 1 atm hydrogenation can be succesfull, it would be good news! But to be honest, I remaing sceptical. No offense DNA, it just that there
isn't much to back up such a possibly ground-breaking news.
[Edited on 4-3-2008 by Klute]
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DNA
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As I stated that paper does work where nitrostyrene is converted to the amine...
I do need to mention I didn't acurately measured the Pd/C and threw a scoop in there since I used quite a small amount to test the reaction, that
could be the cause that there is a lot Pd/C in there and not 10% by weight.
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Klute
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What amount of nitrostyrene did you start with? If you used 0.1-0.5g substrate, I can understand you used a large amount of catalyst... But even 0.5g
is quite an amount, especially considering the price .
BTW, I have been kindly notifyed that catalytic hydrogenation of nitrostyrenes at 20-30°c and 60PSi with as less as 2% 5%Pd/C gives good yeilds in
2h. Obviously one needs a Parr shaker or similar device....
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