Sciencemadness Discussion Board - Al/NiCl2*6H2O: OTC hydride-like reactivity

Al/NiCl2*6H2O: OTC hydride-like reactivity

clearly_not_atara - 12-4-2016 at 13:42

http://www.sciencedirect.com/science/article/pii/S0040402001...

Among the properties: reductive amination, reduces anhydrides to aldehydes, reduces sulfoxides to sulfides in presence of ketones, nitriles to amines, nitroolefins to carbonyls (Nef reaction), aromatic aldehydes in presence of aliphatic aldehydes; halides and unactivated alkenes are unaffected. The abstract claims that aliphatic nitro groups are not affected by the reagent (which can be useful, but reducing them isn't bad either) but no examples involving aliphatic nitro compounds are given.

Et2O is used instead of THF in some examples and gives a similar yield. DMF and chloroform perform albeit poorly. Other ethereal solvents probably work. Alcohols work, but strangely, giving e.g. the reduction of benzaldehyde to benzyl ethers.

And I don't really have a point but I was going to save this anyway, so, yeah.

Quote:

To a freshly mixed solid mixture of aluminium powder (10 mmol) and nickel chloride hexahydrate (15 mmol) is added a solution of the substrate (0.3 mmol) in freshly distilled THF. A vigorous exothermic reaction takes place after a few seconds which subsides after 10 minutes. When TLC of the reaction mixture showed disappearance of the starting material the reaction mixture is diluted with THF (100 ml) and filtered. Evaporation of the filtrate gave the reduced products which are purified further by chromatography.

Attachment: sarmah1991.pdf (747kB)
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[Edited on 12-4-2016 by clearly_not_atara]

[Edited on 12-4-2016 by clearly_not_atara]

DrMethyl - 13-4-2016 at 01:24

Hello, very very interesting info !

I think it works the same way as Al/Cu or even Al/Hg.

I wonder wheter this system will reduce nitrostyrene efficiently. The good point is it seems to work well on simple nitro reduction.

Need a try !

Alkoxide - 13-4-2016 at 03:52

That definitely looks useful! No exotic chems needed and it has good yields for a wide variety of reactions.

[Edited on 13-4-2016 by Alkoxide]

DraconicAcid - 13-4-2016 at 07:02

I wonder if that could reduce esters. I've got lots of methyl salicylate, and would love some salicaldehyde.

clearly_not_atara - 15-4-2016 at 13:23

Quote: Originally posted by DraconicAcid

I wonder if that could reduce esters. I've got lots of methyl salicylate, and would love some salicaldehyde.

You can't reduce the ester directly, but you can reduce it to salicylaldehyde by converting to the anhydride with acetic anhydride, if we assume the reduction of anhydrides generalizes to mixed anhydrides (which seems likely). There will be some over-reduction to salicyl alcohol, but e.g. phthalic anhydride gave 60% of phthalaldehyde and 20% of phthalyl alcohol, with the mixed alcohol-aldehyde apparently a minor constituent.

[Edited on 15-4-2016 by clearly_not_atara]

DraconicAcid - 15-4-2016 at 13:29

Quote: Originally posted by clearly_not_atara

Quote: Originally posted by DraconicAcid

I wonder if that could reduce esters. I've got lots of methyl salicylate, and would love some salicaldehyde.

Surely the reaction of methyl salicylate with acetic anhydride would result in acetylation at the phenolic oxygen?

clearly_not_atara - 15-4-2016 at 15:37

Yes; you would need to first form the Na salicylate or similar by hydrolysis, or start from aspirin which is likely much better in this case. Sorry, I hadn't had my coffee.

tshirtdr1 - 15-4-2016 at 15:45

Wow! Thanks for sharing! I am always trying to save a buck. Does anyone have the full text?

clearly_not_atara - 15-4-2016 at 15:49

Fulltext is attached at the bottom of the OP.

tshirtdr1 - 16-4-2016 at 15:32

I see it now. Thanks.

Chemi Pharma - 7-5-2016 at 11:06

Better use NaBH4 + NiCl.6H2O in methanol. Nickel Boride formed in situ is as powerful as LiALH4, with more selectivity.

See the papers i posted below:

Attachment: Amino acids reduction with borohydride-nickel chloride.pdf (93kB)
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Attachment: nitrile-2boc-amine.nabh4-nicl2.pdf (198kB)
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Attachment: Nitriles to Amines with NaBH4 + NICL2- Nickel Boride.pdf (39kB)
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Attachment: Reduction Of Aliphatic Nitro Compounds To Amines Using NaBH4_NiCl2 and Ultrasound.pdf (157kB)
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Attachment: Sodium Borohydride-Nickel Chloride-Methanol Catalytic System.pdf (279kB)
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Attachment: sodium borohydride-nicl2.pdf (399kB)
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[Edited on 8-5-2016 by Chemi Pharma]

DFliyerz - 25-5-2016 at 10:19

Definitely looks good! When I have time I'll try it with methanol and nitrobenzene.

Eddygp - 25-5-2016 at 12:23

That sounds brilliant! It's sort of reminiscent of the nucleophilic hydrides in NaBH4 compared to the basic ones of NaH.
Nice stuff!

prettypolymer - 26-5-2016 at 06:38

Did anyone try this? Is NiCl2 even soluble in THF?

Polysialate - 5-6-2016 at 18:40

This seems like it would produce some really high-activity nickel (nanoparticles? nanoporous foam?) as the aluminum reduced the nickel chloride. I'm somewhat surprised that it works with the hexahydrate, though I guess the hydrogen for reductions has to come from somewhere. Pretty neat, though I would love to know more about the mechanistic details in this system...

byko3y - 6-6-2016 at 13:56

I'd say the actual catalyst-reagent is just a low activity nickel microparticles, thus stochiometric amount is usually required. Some stabilization agent might provide access to high activity nickel nanoparticles.
Anyway, high activity raney nickel is much more active than a usual Urushibara catalyst (it's an accepted name of the Al-NiCl2 stuff), while very fine nanoparticles have reactivity similar to raney, but usually nanoparticles cannot be reused.

notoxicshit - 14-6-2016 at 05:17

This seems to be what Urubashi catalyst is. And as far as I have heard, it doesn't reliably reduce nitrostyrenes.

It would be very nice to hear of any success reports.

Any alternative solvents known?

clearly_not_atara - 14-6-2016 at 09:45

The Japanese papers claim that the reagent converts nitroolefins to carbonyl compounds. In this case it appears the reaction proceeds by reducing a nitroolefin to a nitronate followed by hydrolysis of the same.

The reaction is not an imitation of Urushibara nickel or other nickel-based hydrogenation catalysts; it clearly happens differently. In particular urushibara catalysts will not selectively yield aldehydes.

If Urushibara nickel does have similar activity to this catalyst, I would expect the reduction of nitroolefins to yield alcohols via reduction of the carbonyl formed by the Nef reaction. Since alcohols are usually undesirable this would explain why Urushibara nickel has a bad reputation in this reduction.

One particular application of the reductant mentioned in the original paper is the reduction of phthalic anhydride to phthalaldehyde, which can then be chlorinated to phthaloyl chloride, a reagent capable of some interesting transformations (in one embodiment converts N-isopropylisobutyramide to 1,1,4-trimethyl-2-chloro-3-aza-2-pentene).

[Edited on 14-6-2016 by clearly_not_atara]

CRUSTY - 14-6-2016 at 17:00

Quote: Originally posted by DrMethyl

I think it works the same way as Al/Cu or even Al/Hg.

Al/Cu? I haven't heard of that one, is its function similar to Al/Hg? I couldn't find any references to it anywhere.

Crowfjord - 14-6-2016 at 17:35

See the thread on Al/Cu here

clearly_not_atara - 12-7-2016 at 13:59

Quote: Originally posted by Chemi Pharma

Better use NaBH4 + NiCl.6H2O in methanol. Nickel Boride formed in situ is as powerful as LiALH4, with more selectivity.

One thing you forgot to mention is that Ni2B is a catalyst, not a reducing agent. It therefore doesn't make sense to compare it to this system, which comprises stoichiometric nickel, because NiCl2 + NaBH4 can be used with catalytic loading using isopropanol as the terminal electron donor. This is a huge improvement in both cost and work-up, but it's also a completely different reaction, and doesn't really belong in this thread. I wish you'd posted this on its own.

In fact the best preparation might use anhydrous NiCl2 and NaBH4 to precipitate a black powder. Ammonium formate/MeOH is an effective hydrogen donor. Isopropanol has been reported to work alone:

http://onlinelibrary.wiley.com/doi/10.1002/aic.690120220/ful...

https://en.wikipedia.org/wiki/Nickel_boride#Catalytic_hydrog...

http://chemistry.mdma.ch/hiveboard/novel/000380497.html

https://www.erowid.org/archive/rhodium/chemistry/nitrile2ami...

The reduction of oximes with Raney Ni/2-propanol has been reported, but I haven't heard of a similar prep using nickel boride. Nonetheless, theory indicates it works.

Chemi Pharma - 12-2-2017 at 13:05

Quote: Originally posted by clearly_not_atara

Quote: Originally posted by Chemi Pharma

Better use NaBH4 + NiCl.6H2O in methanol. Nickel Boride formed in situ is as powerful as LiALH4, with more selectivity.

Funny, the wikipedia link you posted says that Ni2B is a catalyst and also a reducing agent at the same time.

Actually, the reductive power of the mix Ni++ and BH4- is derivated from the nascent atomic hydrogen generated in situ from the reaction and not from the Ni2B. Experiences showed that after 30 minutes the Ni2B precipitaded from the reaction didn't have a half of the reducing power expected.

You can read this on the papers i brought before, that i posted here, in this thread, cause I think Al/NiCl2 technique is surpassed and represents the old school way, in terms of costs and yields, since the use of transition metal borohydride in reductive synthesis has it's use increased a lot in the last decade by the pharmaceutical industries.

At least, it's the direction given by the academic books.

clearly_not_atara - 14-2-2017 at 12:20

Most metals are reducing agents. I'm not sure what your point is. Sodium borohydride (alone) is acceptable for a lot of this stuff but this thread is about people who don't have borohydrides, which are relatively difficult to make.

Also I think it's pretty unlikely you're going to get some of the transformations noted above with borohydrides, particularly the conversion of anhydrides to aldehydes, which can become a conversion of acids to aldehydes if you have acetyl chloride handy. Stronger isn't always better.

Quote:

Funny, the wikipedia link you posted says that Ni2B is a catalyst and also a reducing agent at the same time.

Quote:

Ni2B is an efficient catalyst and reducing agent. It is used as a heterogeneous hydrogenation catalyst.

Is this one of those cases where I'm arguing with someone who's *really* bad at understanding how meaning derives from context, or do you just intentionally misinterpret things in ways that you think might make you sound intelligent? Do you see *any* examples using Ni2B as a reducing agent on its own?

[Edited on 14-2-2017 by clearly_not_atara]

Cryolite. - 14-2-2017 at 17:28

That reactivity looks good, but I'm concerned about the massive excess of reducing agent used to effect the transformations. Could this be scaled down? Nickel salts aren't cheap!

Also, do you know anything about the mechanism? The aluminum and nickel chloride used are in a ratio which will go stoichiometrically to aluminum chloride and nickel metal, which seems suggestive but I'm not sure of what.

Chemi Pharma - 20-2-2017 at 04:23

Quote: Originally posted by clearly_not_atara

Most metals are reducing agents. I'm not sure what your point is. Sodium borohydride (alone) is acceptable for a lot of this stuff but this thread is about people who don't have borohydrides, which are relatively difficult to make.

Also I think it's pretty unlikely you're going to get some of the transformations noted above with borohydrides, particularly the conversion of anhydrides to aldehydes, which can become a conversion of acids to aldehydes if you have acetyl chloride handy. Stronger isn't always better.

Quote:

Funny, the wikipedia link you posted says that Ni2B is a catalyst and also a reducing agent at the same time.

Quote:

Ni2B is an efficient catalyst and reducing agent. It is used as a heterogeneous hydrogenation catalyst.

you'd better be more polite with other members at this forum. I don't understand why you are offending me. I don't want to be cleaver than no one. I just bring new knowledge to the chemistry community and just point the techniques I judge obsoletes.

If you think i commit any transgression, claims for a moderator.

Borohydrides are sold by Aldrich to anyone at anywhere in this world, cause they're not forbidden, they're only watched, even if you live at USA. People that don't have acess to borohydrides are unknowed for me.

Urushibara nickel and al/nicl2 are surpassed techniques and i think it's my duty bring this knowledge to the chemistry community, here at sciencemadness.

I don't care if you think Al/NiCl2 and NaBH4/NiCl2 envolves distincts mechanisms, cause i'm worried with the results, not with it's an eletrophilic, nucleophilic, or sn1 or sn2 reaction. I'm a practical researcher, not a theorist.

For me this theory it's a pure sheet, although i'm graduate in chemistry. What's important for me it's the pratical results and the yields, cause sciencemadness is a forum where people are looking for results, for recipes, not about the beautiful theories you enjoy to learn.

you seems like a professor I had, that's only worried with the chemistry theory, but incapable of building a chemistry production plant.

I don't matter if people are making drugs with this knowledgment, or if they're killing or poisoning himselves dealing with chemicals withouth the apropriate care.

I'm interesting in discuss the newer techniques to sinthesise new pharmacologic drugs and I will give my opppinion and bring new papers and studies anywhere at this forum where i think it's necessary, whatever you think about.

Texium - 21-2-2017 at 20:40

Quote: Originally posted by Cryolite.

That reactivity looks good, but I'm concerned about the massive excess of reducing agent used to effect the transformations. Could this be scaled down? Nickel salts aren't cheap!

Also, do you know anything about the mechanism? The aluminum and nickel chloride used are in a ratio which will go stoichiometrically to aluminum chloride and nickel metal, which seems suggestive but I'm not sure of what.

I was wondering the same thing. I read the whole paper and was quite excited until I got to the end and saw the 50 eq. of nickel chloride for every eq. of substrate...

I suppose it wouldn't hurt to test with different ratios. When I have time in my home lab again, I'd be happy to try reducing benzophenone to benzhydrol using the method. I can bring it back to the university with me and check if it's gone to completion using IR.

Loptr - 15-3-2019 at 17:49

The title of the paper claims it is a neutral reducing systems, so my mind immediately wonders what would happen if the systems were made basic or acidic. Nickel catalysts seem to really like basic conditions.

What bases and acids could be used for this purpose? My initial thought for an acid would be acetic acid, but what about the base? Thoughts?

fusso - 15-3-2019 at 20:45

NaOAc?

TheMasterOfTheInternet - 16-3-2019 at 18:50

Quote: Originally posted by Loptr

The title of the paper claims it is a neutral reducing systems, so my mind immediately wonders what would happen if the systems were made basic or acidic. Nickel catalysts seem to really like basic conditions.

What bases and acids could be used for this purpose? My initial thought for an acid would be acetic acid, but what about the base? Thoughts?

Nickel catalysts do love basic-, like neutral- but seriously hate acidic conditions in my experience. Simply because the large super reactive surface of the Ni0-particles is etched away even by quite weak acids, yielding non-active Nickel(II)-salts again.

If your reaction needs acidic conditions, you have to use Pd, Pt, Ru, Au,...

clearly_not_atara - 14-9-2023 at 15:12

Years ago I posted this thread without thinking too critically about the stoichiometry issues (massive excess of Ni, Al). Recently however I found a much more efficient method for obtaining similar reactions. Bodnar et al use 2g Ni and 6g Fe to reduce 5 grams of benzonitrile to the aldehyde in 89% yield, if I'm reading this correctly. Aliphatic nitriles are also reduced to aldehydes under the same conditions. Unfortunately, the authors use mass rather than moles to quantify reagents, which is wrong, but the rest of the work looks solid.

This is achieved by treating a suspension of the sacrificial metal with a solution of nickel salt, which results in a coated powder that has high(er) reducing activity.

This paper investigates only reductions of nitriles to aldehydes, but the methods may translate to other reactions. It appears that the use of aluminum instead of iron results in other reduction products (the primary or possibly dimerized secondary amine).

Attachment: bodnar1991.pdf (1.7MB)
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EDIT: A companion study by Mallat et al (same team) also documents the reduction of many other substrates with similarly constructed systems. Unlike the majority of mercury-free dissolving-metal reductions, the stoichiometry is reasonable.

[Edited on 15-9-2023 by clearly_not_atara]

Attachment: mallat1991.pdf (657kB)
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