tsathoggua1
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Re-usability and practical experience with nickel boride reductions.
Will rephrase my earlier thread that got moved to detritus (and I should state that most of what I wanted to know was the likely source of the color,
be it partially reduced polymeric side products, since some Ni2B/NaBH4/MeOH systems [which have, by the way, proven to reduce both aliphatic and
aromatic nitro groups and aliphatic alkenes, neither borohydride alone nor Ni2B alone, in MeOH, as per this paper solo posted:
http://www.sciencemadness.org/talk/files.php?pid=82363&a... )
Contrary to what was said by one member, methanol actually appears to be the better solvent to use, with byproducts being reported when EtOH or iPA
were used. There are plenty examples of aliphatic alkenes around using the borohydride/Ni2B/MeOH system, and also its known to reduce oximes to
amines. So is it so far fetched that it would reduce an aliphatic nitroalkene all the way to the corresponding aminoalkane?
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laserlisa
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NaBH4 and Nickel boride will reduce nitroalkenes to aminoalkanes. I think there are some successfull attempts reported at hyperlabs if Im not
mistaken.
[Edited on 3-6-2017 by laserlisa]
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Metacelsus
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Nickel boride will reduce conjugated alkenes, from personal experience (the specific example was a stilbene). The solvent was a 1:1 mixture of THF and
methanol. The stilbene reduction was actually a side reaction which I had been trying to avoid, since I was using the nickel boride for
desulfurization.
I have not tried it with nitroalkenes.
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tsathoggua1
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Its just that somebody specifically stated that, in a post that got canned, presumably thought it was a request for spoon-feeding (actually, what I
wanted to know, specifically, was the nature of a pink-peach tint that forms, at least when the MeOH has not been stripped) on acidification with
strong acids (E.g HCl, as yet haven't tried a weak acid such as AcOH), whether it is a nickel compound/nickel-boron compound, boron compound or
whether it is an organic, dimeric species. The catalyst in my experiments thus far with it, is of P2 type, using MeOH rather than EtOH as solvent (bar
DIY fermentation and distillation or distilling commercial spirits its much more practical, or alkaline cleavage of EtOAc, of which I have currently
very little), whilst the american members might have access to strong grain alcohol of the 'everclear' type, we brits on the other hand, do not. It
just isn't sold here that I have ever heard of. There are some really quite expensive top of the line vodkas that are 40% or just above that but
usually its about 35% EtOH, and don't have the money to buy any anyway, so methanol had to be tried)
One poster in the first thread I tried to start on Ni2B specifically stated that despite in most cases MeOH being suitable for replacing EtOH in many
reactions, nickel boride reductions in particular wasn't one of them. Yet MeOH seems to be the most common solvent used in references to Ni2B/NaBH4
reductions. Presumably the poster in question erred in their statement. What I'd like to know is why they think it unsuitable.
The catalyst formed, alright, same as described in EtOH, as a fine, grey-tinted black suspension, which sinks, eventually, and permits decantation of
the product or products of reaction in the methanolic layer and the paper I posted, and there are others (one I can't post, since I only have a
hardcopy) that describe oxime reductions, and simple aliphatic double bond reductions.
Anyhow in the other thread
Hyperlabs isn't much use to me lisa, I'm afraid I don't speak russian, a few words but nowhere near enough to be able to read the vast majority of
postings.
One other thing I'd like to know, is assuming the catalyst hasn't been in direct contact with air, a single quantity should be suitable for re-use a
few times without dramatic drop in yield. How does (with any substrate, nitroalkenes, nitroalkanes, plain alkenes, desulfurizations [does the sulfur
poison the catalyst in these?] anything at all, how much use can one get out of a single batch of catalyst?
[Edited on 3-6-2017 by tsathoggua1]
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Melgar
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I was the "the poster in question", and I linked you to this paper that explains what happens when you combine MeOH and sodium borohydride:
http://pubs.acs.org/doi/abs/10.1021/ja00865a003?journalCode=...
The paper you linked (actually the Rhodium version, saved as a PDF for some reason) described reduction of nitroalkanes, not
nitroalkenes, and also used ultrasound, which you didn't mention having used. Here's the link to the web page it was saved as a PDF
from:
https://erowid.org/archive/rhodium/chemistry/nitro2amine.nab...
Reducing the double bond there is actually the hard part. Nitro group reduction after that is a lot easier. What you are describing is the reaction
of sodium borohydride with methanol in the presence of a nitrostyrene/nitrophenylpropene. I can't speak for the nickel, except to say that you would
get that same reaction in its absence.
Edit: Extrapolations like you've made have to be tested experimentally, and it sounds like the results of the experiment haven't been successful. The
typical method for doing what you're obviously trying to do is to first use sodium borohydride to reduce the double bond, which it can only do because
of the nitro group there. That is the only reduction that sodium borohydride can do, which is convenient, because then you can reduce all the
nitroalkenes to nitroalkanes without getting any further-reacted products that would add to unreduced double bonds. So to get the highest yields,
it's done in two steps. The second step is just to reduce the nitroalkane, which can be done using any of a number of different reagents.
[Edited on 6/5/17 by Melgar]
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Corrosive Joeseph
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Paper now attached -
/CJ
Attachment: davis1962.pdf (535kB)
This file has been downloaded 531 times
Being well adjusted to a sick society is no measure of one's mental health
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tsathoggua1
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The experimental method being tested is (using the nitroalkene) preforming P2 nickel boride although using methanol in place of EtOH. The salt chosen
is nickel (II) acetate. From the description of nickel boride (fine, dark powder when generated, or if bought from suppliers then dark black granulat
material) the product of borohydride addition to the Ni (II) acetate (seemingly the results of using NiCl2 vary vs the acetate, although a paper I
only have in hardcopy, and unfortunately does not have the DOI on the pages I have, printer seems to have trimmed the end off at the very bottom,
produce catalysts that differ somehow in selectivity) As of yet I know little about P1, no practical experience with it anyway, I figure I'll
investigate P2, and then move on to P1 and make comparisons, repeat the same set of experiments, as well as using EtOH to form the catalyst and as rxn
solvent for P2)
It does appear to form. And it does appear to reduce the nitro group. If needs be I can make it a two-step reduction, first reducing the substrate to
the saturated nitroaliphatic homolog of the nitroalkene being tested as a substrate. mono-nitrotoluene would be the only other substrate I currently
would have the stuff on the shelf to test, but there are some caveats in particular with Ni2B-P2 (the alcoholic media version) in that it reportedly
will not perform hydrogenolyses at least, upon benzylic substituents other than IIRC, esters, allylic or propargylic sites. Not sure if this applies
also to P1 type nickel boride, reportedly Ni2B P2 is quite sensitive to steric hindrance and in some cases (I need to track down a specific reference
to find out which ones and why) to the nature of the alkene. But it is stated to reduce both aliphatic nitro groups and aliphatic alkenes.
Will add to post when more PC access available. Plus experimental data.
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zed
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Well, back a million years ago, when I tried those reductions, they did not work.
Tried Nickel, Tried Cobalt, Etc..
Nitro-propenes like to be reduced in an acetic environment. Reduces polymerization.
Those Borides don't like an acetic environment.
Also, attempted these reductions utilizing Pt.
In no case, was I successful in producing Phenyl-isopropylamines. Some reductions proceeded smoothly to the oxime. And, that was it. Actually
worked best with Pt in an acetic environment. Boride reductions in neutral or basic solutions, produced crud, but no amines.
Now, the reduction of the Carbon-Carbon double bond, via borohydride.......Followed by hydrogenation of the Nitro-Alkane, might work. In my day,
that C=C Borohydride reduction, was not known.
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Melgar
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Ok, I think you might be making a few invalid assumptions, so I'll just throw out a few facts that you, or someone else reading this thread, may have
missed at some point:
1. Different reducing agents preferentially reduce different groups, and their preferences can vary a lot based on what groups are adjacent to those
groups. These preferences have been determined experimentally, and there isn't always a good theory that explains why certain reagents work the way
they do. It's not enough to see a certain structure in a molecular diagram and think that you have something that will reduce it. Take the double
bonds in benzene, for example. So when you have a double bond that's adjacent to both a ring and a nitro group, (both groups that are known for
interfering with adjacent group functionality), it's a pretty good bet that it's going to need different conditions than say, reducing propylene or
styrene.
2. If something is attached to a ring, everything changes. More changes for aromatic rings (rings in which all the members share electrons) than
aliphatic cyclic structures, and heterocycles (rings containing atoms besides carbon) all have their own names and branches of chemistry because of
the considerable differences in their reactions.
3. Use easily-obtained reagents first, that don't react to produce something illegal in your jurisdiction. The police aren't going to accept
"nitroethane was the only nitroalkane I had" as an excuse when they find 20 grams of amphetamine freebase and 150 grams of P2NP in your possession,
and enough chemicals to make 1-2 kg more. In the US, they'd parade you in handcuffs and a prison jumpsuit, in front of all the local reporters from
every newspaper and TV station in the city, boasting about how they've racked up another win in the War on Drugs. Then they'd throw you in prison at
least until a sympathetic Democrat is elected president (or governor, if you ran afoul of state law; you'd be FUCKED in most of the south), serves out
most of his (or her) term, and is about to leave office. Of course, you're obviously not in the US, but I'm pretty sure homemade amphetamine is
illegal in all of Europe too.
[Edited on 6/7/17 by Melgar]
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zed
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Yet, not all analogs are illegal everywhere. As several board members, in the far-East and other locales, have informed me.
And, some of our posters, work in academic or industrial environments, where the requisite permits are present.
I try to assume, that folks have their paperwork in order.
Otherwise, the above cautions DO apply. And, in many jurisdictions, punishments are more extreme than they are in the U.S..
Personally, I conducted most of my experiments under an "Academic Umbrella". And, as such, I avoided notoriously illegal analogs.
This is an interesting area of study. But, as a gentleman, one should at all times, avoid the appearance of impropriety.
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tsathoggua1
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Cobalt boride, Melgar, is known not to reduce nitro compounds alone, with H2, or borohydride.
Also, I am aware of points 1 and 2. And 3 for that matter (although are correct, I am not an american, so points/practices and policies which
specifically apply only within the US, of course do not apply.)
With regards to reducing nitroalkenes, yes chances are, certainly with P2 type catalyst that pre-reduction of the aliphatic double bond would be the
superior way. This is more about figuring out the chemistry. And evaluating what sort of scope these nickel borides have for use in any aspect. And
Zed-was it solely the boride that was tried? (or boride/H2) or was it a boride/borohydride scheme that you had trouble with? they are known not to
reduce nitro groups to amines alone, although it is surprising that, if using Ni2B/borohydride or Ni2B/borohydride/H2 that there was not reduction of
the oxime to the amine. What ratios of borohydride to substrate were used? because it takes quite a lot, 10.4 mol. eq. or so. But I have read a paper
claiming very good yields of various amines via reduction of the corresponding oximes.
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zed
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Times change. Discovering optimal reaction conditions, can take a few lifetimes or so.
In those days, I was pretty much prowling, in an unknown area of the woods.
So, you have a link to that paper, or is it the one that I so blithely passed by at the top of the page? I'll check.
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tsathoggua1
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I don't, unfortunately. I only have a printed copy, but if you want, I can have a look around and try to find it again zed?
Although it might take me a while, I'm quite busy atm. And will have to re-do my experiments with the P2 boride, since somebody knocked over the flask
containing the post-rxn mixture although the substrate is available for another attempt. Although that must wait until the end has been met via the
ketoxime and Na/iPA.
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