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Author: Subject: Pd/C H2-gas reduction of ß-nitrostyrenes
Palladium
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[*] posted on 8-6-2011 at 03:13


Quote: Originally posted by Nicodem  
It pretty much depends on what you are hydrogenating. For example, if you are hydrogenating an isolated olefinic double bonds which reduces already at 1 atm, increasing the pressure is not going to help much. Nitroarenes also don't need increased pressure and 1 atm does just fine. But if you are reducing groups difficult to reduce using Pd-C (e.g., nitriles, oximes, debenzylations, some aryl alkyl ketones, dechlorinations), then it is well worth speeding up the reaction by increasing the pressure. But in essence, whatever works in a Parr shaker apparatus (designed for 60 PSI = 4.14 bar) will work also using a balloon as long as you load it up with some more catalyst (and/or use the 10% Pd-C) to compensate for the slowing down.

On the other hand, hydrogenations in autoclaves at >100 bar with heating up are something quite different. Usually things that refuse to get hydrogenated in a good ol'shaker apparatus, will eventually give up under such forcing conditions. But these are usually employed when using catalysts like copper chromite, or for the reduction of benzene rings with Ni or Pt based catalysts.

For the more common transformations, you can always choose a more appropriate catalyst instead of forcing conditions. For example, if neutral or basic conditions are tolerated, you can often choose Raney Nickel over Pd-C. As an example, nitriles reduce sluggishly with Pd-C in the presence of HCl, but the same transformation can be performed better with Raney Ni in the presence of ammonia at the same pressure. Furthermore, since the Raney Ni is cheap, you can use lots of it, thus making the reaction proceed faster at a much lower pressure.

In the case of beta-nitrostyrenes, I would expect a slight complication when the reaction is too slow. Lowering the pressure without increasing the catalyst load, will slow down the hydrogenation, but it will not slow down any side reactions that do not involve hydrogen (like the hydrolysis of some intermediate, for example). I believe this might be the reason why the Japonese authors perform the reaction at 0 °C. I also believe this is why, in the above mentioned patent, increased temperatures can be used to force the reaction on a nitropropene - no acid is being used. This probably reduces the selectivity for the primary amine, but at least it allows for harsher conditions. The claim that the reduction goes better with a mixture of Ni and Pd based catalysts might have a rationale as well. The Pd catalyst might reduce to a certain stubborn intermediate which is on turn further reduced by the Ni catalyst (the oxime?).


I would like to ask one thing about the solvent used in hydrogenation. I know it works with a number of solvents, but I thinking of if some denaturants can affect the reaction. In my case the denaturant is 2-butanone. I have problems to believe this would make any difference, but I will still exclude this suspicion.

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[*] posted on 19-6-2011 at 14:53


here is some further information on this and explains why normal pdc is not very usefull

regards azo:D

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[*] posted on 20-6-2011 at 12:33


Quote: Originally posted by azo  
here is some further information on this and explains why normal pdc is not very usefull

regards azo:D


Thanks a lot for this. Pd/C is king when it comes to OH-reduction I suppose, but still sensitive.

I will build my setup for Raney Nickel reduction. The melting isn't that difficult, and not the agiator either. 80 bar pressure isn't so much anyway. Still, it is a lot of work. After a lot of research on RaNi I find that this catalyst is essential and high-yielding in many cases. Surprisingly cheap catalyst also, probably possible to reuse also.

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[*] posted on 23-6-2011 at 03:13


Here is a little on urishabara palladium


regards azo:D

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[*] posted on 28-12-2014 at 05:42


Quote: Originally posted by Nicodem  
Quote: Originally posted by Palladium  

1. I followed the example in the link exactly, but used a normal 5% Pd/C catalyst, not in the report mentioned "5% Pd/C K-type" - which I can't find any further information about anywhere. I can tell you flat out that this process doesn't work - at least not with a normal Pd/C catalyst.

I don't understand why it would not work for beta-nitrostyrene when it works for methoxy substituted beta-nitrostyrenes. How sure you are you that your Pd-C is still active? How did you verify the purity and identity of your beta-nitrostyrene? Is your HCl free of H2S?

Quote:
Notice that they are using relatively large amounts of catalyst (200 g Pd/C 5% per mole PEA), probably because the Pd/C is undermined in efficiency at 0 °C compared to higher temperatures. I tried this reduction at 2-5 °C in EtOH and HCl (aq) at 1 atm H2-pressure in 3 h. No noticeable reaction; in fact, all of the ß-nitrostyrene was left when solvent was removed - and after heating much of this will polymerize.

As the experimenters at the Hyperlab forum demonstrated, the amount of the catalyst can be reduced to 5 mol% (or even less, highly depending on the substrate) and still obtaining good yields provided you use pressure in the range of 2-5 bar and start with a cold mixture. My memory is not very good, but I think they used slightly above 1 equivalent of conc. HCl in methanol. I do well remember that lots of substrates have been tested and no reports of failure mentioned. Check by yourself as I have no time to search info for you. I remember there is also an example of an arylacetonitrile hydrogenation with Pd-C. Most posts are in English so you should have no troubles with the search engine.

Anyway, the HCl is used to prevent the formation of secondary amines by in situ amine protection. Secondary amines form during the reduction of oximes and nitriles in the absence of added acid (see Hydrogenation Methods by Rylander). Since the reduction of beta-nitrostyrenes gives first the phenylacetaldoximes which are then the difficult ones to reduce (can be even preparatively isolated in good yields as is described in some articles), the acid can cause troubles due to partial oxime hydrolysis, especially if the temperature is higher. Aldoximes reduce slowly with Pd-C (contrary to their reduction with Raney nickel which is very fast) while, as far as I know, ketoximes are nearly impossible to hydrogenate with Pd-C. This slow reduction step is probably the reason for the high dependence of yields on the catalyst loading. If there is not enough Pd-C, much of the oxime intermediate hydrolyzes before getting reduced to the amine. I'm mostly guessing from the results described in the few articles on the topic, that I read (years ago, so don't rely to much on what I say).


nicodem, would you be able to provide clues as to the wherabouts of the experimental trials undertaken at the hive? I cannot find any, only reference to the atmospheric reduction undertaken at the start of the thread.




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[*] posted on 29-12-2014 at 07:54


Quote: Originally posted by Templar  
nicodem, would you be able to provide clues as to the wherabouts of the experimental trials undertaken at the hive? I cannot find any, only reference to the atmospheric reduction undertaken at the start of the thread.

I can only assume that I meant Hyperlab when I referred to Hyperlab. Where did you see The Hive mentioned? That forum is dead for 10 years already.
Quote: Originally posted by Nicodem  
As the experimenters at the Hyperlab forum demonstrated...
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[*] posted on 29-12-2014 at 15:03


These reductions run well in glacial acetic with an equivalent of H2SO4 added.

[Edited on 29-12-2014 by zed]
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[*] posted on 29-12-2014 at 15:28


Sorry, that was a small typo. I did mean hyperlab.



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[*] posted on 29-12-2014 at 16:00


You are assuming that such experiments were actually performed?

That may be an error. Some of the experiments reported on the "Hive" as dreams, were just that....dreams. Pipe dreams to be more exact.

B Nitropropenyl benzenes, also polymerize during the reduction. Since no aldehydes and no amines are formed during the initial stages of the reduction, it clearly isn't formation of secondary amines , but is some other phenomena.

Without temperature control, a solvent consisting of 50/50 methanol- glacial acetic acid, will produce about a 50/50 yield. 50% Oxime, 50% brown crud.

With temperature control, utilizing Glacial acetic acid and an equivalent of H2SO4; yields of Oxime appear to be ~90%, without traces of crud. Product solutions are basically colorless. This is using a "Brown" type Pt as catalyst.

[Edited on 30-12-2014 by zed]

[Edited on 30-12-2014 by zed]
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[*] posted on 29-12-2014 at 16:19


Quote: Originally posted by zed  
You are assuming that such experiments were actually performed?

That may be an error. Some of the experiments reported on the "Hive" as dreams, were just that....dreams. Pipe dreams to be more exact.


Yes. I did sort of guess that. It sounded like they had been completed experimentally and that someone had read them. I cannot find them; but Ihave a hunch that there are some sections of that forum I cannot see.

I am trying to sort a hydrogen regulator. Getting prices of $300-500! Im in NZ. So I will need to find one overseas maybe that will be compatible with the canister threads available.

The next issue to sort will be a suitable vessel. A friend of mine suggested that a pressurized vessel like a weed sprayer could be useable. I want to try and find pressure rating for them; easier said than done.

I think the main issue here isnt so much a tough container as it is finding one that can be modified for the fittings off the h2 canister.

I was shown a fairly basic but effective shaker design, so I will run with that.

So zed, you are reporting oximes instead of amines?

[Edited on 30-12-2014 by Templar]




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[*] posted on 29-12-2014 at 16:27


Hnuh? You are actually gonna try it? You need a Rabbi...a mentor. Depending on what exactly you wish to do, you may need a permit. The experiment is easily performed, with a little platinum, a few bucks worth of chemicals, a flask, a balloon, etc.
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[*] posted on 29-12-2014 at 16:39


Quote: Originally posted by zed  
Hnuh? You are actually gonna try it? You need a Rabbi...a mentor. Depending on what exactly you wish to do, you may need a permit. The experiment is easily performed, with a little platinum, a few bucks worth of chemicals, a flask, a balloon, etc.


Ah, well I was hoping on running a low pressure setup at around 3 or 4 bar gauge.

The costs right now are looking a little bit prohibitive though.

I probably wont get involved with any rabbis. I think they have a reputation for doing strange things with young handsome men :o

Its sounding like oximes are obtained at atmospheric pressure using GAA and sulfuric acid? but the oxime is reduced to amine under additional pressure.




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[*] posted on 30-12-2014 at 02:27


Quote: Originally posted by Templar  
So zed, you are reporting oximes instead of amines?

Just as the literature does. The hydrogenation of alpha-substituted nitroolefins over Pd-C to obtain ketoximes is a known synthetic method. Pt catalyst behave similarly.
Quote: Originally posted by Templar  
Its sounding like oximes are obtained at atmospheric pressure using GAA and sulfuric acid? but the oxime is reduced to amine under additional pressure.

Depends which oximes and what catalyst, not so much the pressure. Good luck in reducing regular ketoximes over Pd or Pt catalysts. It can happen to some extent in some cases, but it is not worth optimizing given the alternatives. Even aldoximes are slow to hydrogenate over Pd-C, let alone the ketoximes. Read some literature on hydrogenations. There is a very good book on the topic: Catalytic Hydrogenation in Organic Syntheses by A. Rylander. I suggest you read it thoroughly before you waste time reinventing the wheel (or you injure yourself).
Quote: Originally posted by Templar  
Sorry, that was a small typo. I did mean hyperlab.

Did you search there at all? It does not look like you tried at all. Just by using the keyword "hydrogenation" I got plenty of experimental examples. The most relevant ones are in the thread #514228 and post #550718. There is more in the Development crew forum section. And I only looked for English language. There must be much more to be found with some more effort.

[Edited on 30/12/2014 by Nicodem]
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[*] posted on 31-12-2014 at 15:47


Start small. Aim for a few grams of product. Most experiments fail. Even when there are reliably recorded procedures, a positive outcome is no certainty.

Baby steps. You knew for example, that gauges used with Hydrogen must meet certain materials specifications? Yup. Some gauges have the right kind of guts, some don't. With the wrong kind of innards, your gauges will probably still work, but not for very long.
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[*] posted on 31-12-2014 at 20:48


Quote: Originally posted by Nicodem  
Quote: Originally posted by Templar  
So zed, you are reporting oximes instead of amines?

Just as the literature does. The hydrogenation of alpha-substituted nitroolefins over Pd-C to obtain ketoximes is a known synthetic method. Pt catalyst behave similarly.
Quote: Originally posted by Templar  
Its sounding like oximes are obtained at atmospheric pressure using GAA and sulfuric acid? but the oxime is reduced to amine under additional pressure.

Depends which oximes and what catalyst, not so much the pressure. Good luck in reducing regular ketoximes over Pd or Pt catalysts. It can happen to some extent in some cases, but it is not worth optimizing given the alternatives. Even aldoximes are slow to hydrogenate over Pd-C, let alone the ketoximes. Read some literature on hydrogenations. There is a very good book on the topic: Catalytic Hydrogenation in Organic Syntheses by A. Rylander. I suggest you read it thoroughly before you waste time reinventing the wheel (or you injure yourself).
Quote: Originally posted by Templar  
Sorry, that was a small typo. I did mean hyperlab.

Did you search there at all? It does not look like you tried at all. Just by using the keyword "hydrogenation" I got plenty of experimental examples. The most relevant ones are in the thread #514228 and post #550718. There is more in the Development crew forum section. And I only looked for English language. There must be much more to be found with some more effort.

[Edited on 30/12/2014 by Nicodem]


Yes I am sure you can find a lot of good information nicodem. When you have full access to the forum. There is no development crew section available for me, nor can I message members or make posts. I thought there were not hidden sections but it looks like there are.

I mistakenly thought that there was a procedure in the CTH thread here http://www.sciencemadness.org/talk/viewthread.php?tid=8929
where a nitrostyrene was reduced directly to an amine in a single step procedure. I must have seen a typo or made a mistake.

In regards to the concerns about the adaquate equipment, this is proving to be a concern. Regulators are priced at 300-500$ each here. Additional pressure gauges, tubing and clamps will probably see the whole setup come close to $1000. Finding regulators off ebay at a reduced price may work; if the threads on the h2 bottles available here will be suitable.

Since I do not stand to profit off what is synthesised, this is likely going to be a barrier to doing a pressurized hydrogenation. I will have to save up for a while.







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[*] posted on 1-1-2015 at 00:24


Hydrogen embritrlement...

http://en.m.wikipedia.org/wiki/Hydrogen_embrittlement




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[*] posted on 1-1-2015 at 11:28


Quote: Originally posted by Bert  
Hydrogen embritrlement...

http://en.m.wikipedia.org/wiki/Hydrogen_embrittlement


That is very real. It was a potential, and sometimes real, problem in an electrochemical process I was involved with.
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[*] posted on 3-1-2015 at 14:51


"Yes I am sure you can find a lot of good information nicodem. When you have full access to the forum. There is no development crew section available for me, nor can I message members or make posts. I thought there were not hidden sections but it looks like there are."

Hidden sections? Must be hidden from me too.

More likely, we just have access to longer memories. Since many of us have pondered the current subject, for 10, 20, 30, or even 40 years......we've got a lot of invisible background information, bouncing around inside of our heads.

Cheer up! You are getting the friendly treatment.
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[*] posted on 9-1-2015 at 12:49


Quote: Originally posted by Templar  
Yes I am sure you can find a lot of good information nicodem. When you have full access to the forum. There is no development crew section available for me, nor can I message members or make posts. I thought there were not hidden sections but it looks like there are.

You are talking a lot of nonsense, because it is so obvious to me that you did not check the posts I cited. They are obviously not in any hidden sections. Read my previous reply again. I did not list the ones that are not public.
Quote:
Since I do not stand to profit off what is synthesised, this is likely going to be a barrier to doing a pressurized hydrogenation. I will have to save up for a while.

You would profit more by learning the chemistry of whatever endeavour you are up to. There is a lot of experience published in the scientific literature that you could look up.
Why do you want to use pressure vessels where there is no need for it? You should first practice hydrogenations at atmospheric pressure. Without proper knowledge and experience, you are more likely to get injured or frustrated due to failures.




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[*] posted on 19-2-2016 at 14:41


Reference Information


Beta- Phenylehylamines: THE CATALYTIC HYOROGENATION OF OMEGA- Nitrostyrenes
0.P.Wagner,A. I.Rachlfn
Synthetic communications
1971,1:1, 47-50
doi.10.1080/00397917108081616




Abstract
Good yfelds o f s-phenethylamfne hydrochlorfde oalts are obtafned directly from the catalytic reductfon o f a,3-unsaturatd nitro compounds in dilute hydrochloric acid.

Attachment: php6BgBQP (454kB)
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[*] posted on 19-2-2016 at 17:31


Quote:
To a suspension of X g of an w-nitrostyrene in X mL of conc. hydrochloric acid is added ca. 0.2-0.3g of 10% Pd-C catalyst and enough water to make the w-nitrostyrene comprise 5-7% of the mixture. Reduction is carried out at 50-80º under 500-1500 p.s.i. of hydrogen in an agitated autoclave.


(from the above paper)
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[*] posted on 19-2-2016 at 18:22


.....this may be more approachable with less pressure....solo



Synthesis of Phenethylamines
by Hydrogenation of beta-Nitrostyrenes

Kohno, Sasao and Murahashi
Bull. Chem. Soc. Jpn.
63(4), 1252-1254 (1990)

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[*] posted on 20-2-2016 at 07:08


Reference Information




Iron-catalysed, general and operationally simple formal hydrogenation using Fe(OTf)3 and NaBH4
Alistair J. MacNair,a Ming-Ming Tran,a
Org. Biomol. Chem.
2014, 12, 5082
DOI: 10.1039/c4ob00945b



Abstract
An operationally simple and environmentally benign formal hydrogenation protocol has been developed using highly abundant iron(iii) salts and an inexpensive, bench stable, stoichiometric reductant, NaBH4, in ethanol, under ambient conditions. This reaction has been applied to the reduction of terminal alkenes (22 examples, up to 95% yield) and nitro-groups (26 examples, up to 95% yield). Deuterium labelling studies indicate that this reaction proceeds via an ionic rather than radical mechanism.

[Edited on 20-2-2016 by solo]

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[*] posted on 20-2-2016 at 10:05


.....and of course there is the psyloxy's Hive archive method without gas....solo

-----------------------------------------
psyloxy
(Hive Bee )
6/8/00 07:42 AM

Re: Nitropropene Reduction new [Post#: 15452 ]

What about NaBH4/Pd/C ? This seems to work without pressure and yields around 70%.

------------------------------------------------------------------------------------------
dreamer:


- 0.05mol 8gr beta nitropropene C9H9NO2 63gr/mol
- 13gr 5% Pd-C
- 100ml Methanol
- 50ml THF
- 0.15 mol NaBH4

- 8gr P2NP are dissolved in 50ml THF and 50ml Methanol and is stirred on
a magnetic stirrer
- 1.9gr NaBH4 are slowly added over a period of 30min
- the addition of nabh4 is effervscent
- after 15min of stirring 13gr 5% Pd/C in 100ml methanol is added;
- don't add the Pd/C without solvent, it will catch fire )
- the you should add slowly over a period off 1h (i did it) 4 gr NaBH4;
- reaction is continued for another 3h and 5ml of acetic acid is added
(to neutralize NaBH4 .. maybbe you don't this) and 20ml of 31% HCl and
50ml of H2O;
- the solution turns red
- Pd/c is filtered away and washed with Methanol and dH2O
- Methanol and THF is eliminated, the red color disappears
- all is washed with DCM
- make it basic with 100ml 25%NaOH and extract; you should get around 5gr
of the freebase (i did), yield ~70%; the salt is easily made with H2SO4
in ethanol, but don't add too much H2SO4 or your salt dissolves (if
this happens make all basic and extract)

a few days bevor i tried the same thing with ethanol, yields were much
lower and the addition of NaBH4 was not so effervescent
------------------------------------------------------------------------------------------

--psyloxy--
-----------------------------


.......that's a lot of palladium, for 8 gr....better recycle it , otherwise it's an expensive route.....solo

[Edited on 20-2-2016 by solo]

[Edited on 21-2-2016 by solo]




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[*] posted on 21-2-2016 at 09:35


......there is always the Hive's post, a cooperation of hive members and hyperlab members........solo

--------------------------------------------------


Reduction of Nitroalkenes with Aluminium Amalgam
Translation and Compilation by Antoncho

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[Edited on 21-2-2016 by solo]




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