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Texium
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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.
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Loptr
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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?
"Question everything generally thought to be obvious." - Dieter Rams
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fusso
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NaOAc?
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TheMasterOfTheInternet
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| 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?
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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,...
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clearly_not_atara
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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)
This file has been downloaded 246 times
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)
This file has been downloaded 235 times
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