Reduction of nitroalkenes to nitroalkanes

Is your target the amine though?
Then use the novel one-pot method with NaBH4/CuCl2, it replaced the old Al/Hg for us as the gold standard.
And besides those two methods, there still are others that don't use LiAlH4 for the reduction all the way in one-pot.
And it works not just as well as LiAlH4, it works actually even better, both of them.
And those two, NaBH4/CuCl2 and Al/Hg, are the most popular, with a good third place being stoichiometric_steve's NaBH4/Zn one-pot method, in my opinion.
But I have to add that I am quite well informed on that matter, especially regarding actual developments and how the people are making use of them
Those two borohydride based methods actually use the nitroalkane as intermediate of course, just prepared in-situ.

Yes the Zn/HCl works only on nitrostyrenes but not on a-alkylnitroalkenes.
But on all nitroalkanes it does work very well(thus said mentioned one-pot method using NaBH4/Zn+ammonium formiate), also the one or other method that achieves this in two separate reactions with an isolation of the intermediate.

But this is also popular to do that as two separate reactions, since the nitroalkanes can be reduced in the very huge scalable method employing a hydrogenation under CTH conditions with palladium.
And unlike LiAlH4 reductions which require a large volume, this can be scaled very well, but without being as potentially dangerous as that stuff, yet while resulting in very good yields as well.
Both steps will result in yields of at least 80%, and can be carried out in comparably small reaction vessels because of the mentioned reasons.

If you want to reduce nitroalkenes to -alkanes, there is no other really useful method besides sodium borohydride.
And for those, a preferable method is to do it in a biphasic system with a PTC agent, as this reduces the amount of reducing agent needed, while the need for an overall excess of borohydride is reduced without an increased risk of dimerisation.
The formation of said dimer is an issue if not enough borohydride is employed.

So what is your real question here, or rather, your intention?
I could answer much more precisely and helpful if I just would know more precisely what you want to do?
Surely I can reply in a more useful manner if you tell what it is exactly you want to know.

I've seen Fe/HCl used to reduce nitropropenes, I assume Zn/HCl would also work since Zn has a stronger reduction potential than Fe. Reducing agents like LAH and Red-Al are generally used to reduce nitrostyrenes to amines but CuCl2 and NaBH4 also gets the job done, see http://www.sciencemadness.org/talk/viewthread.php?tid=84596

I'm not sure if Zn/HCl on nitrostyrenes is straight to the amine, there are a number of intermediate steps. Someone uploaded a paper with some theory on it, very interesting read if you like dissolving metal reactions. http://www.sciencemadness.org/talk/files.php?pid=603835&... With that said, I've tried it on vanillin nitrostyrene a few times -- it works, but it's a challenging reaction that requires strict temperature control throughout.

[Edited on 8-31-2020 by monolithic]

Quote: Originally posted by njl

oxime reduction to amine with Zn/ACOH

Quote: Originally posted by njl

Also karlos https://erowid.org/archive/rhodium/chemistry/oxime.txt at the bottom there is a short ref for oxime reduction to amine with Zn/ACOH. Now I know better than to trust a 1 paragraph ref in plaintext, but could there be any credence to this since AcOH is milder than HCl?

Quote: Originally posted by njl

Sort of the other end of the spectrum but it's also pretty crazy how high silver has gone. Are the rising prices due to scarcity or more industrial demand?