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Author: Subject: NaBH4/NiCl2 reduction
brainetix
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[*] posted on 14-12-2006 at 08:34
NaBH4/NiCl2 reduction


John O. Osby and Bruce Ganem
Tetrahedron Letters 26(52), 6413-6416 (1985)

This Article describes the reduction of Nitro compounds with NaBH4/NiCl2 complex of NitroalkAnes. Total Synthesis says you can reduce NitroalkEnes with it. What ist right?

This is for primary amines.... But maybe this should work for secondary ones...:

The boride is prepared like in the article. Then let´s say 10% or so of used Nitromethane in MeOH is added dropwise at rt or slight cooling. MeAm is formed. Then a mix of Ketone/Nitromethane/MeOH is dripped in, while the calculated ammount of NaBH4 was added in portions. The MeAm will condense with the ketone to the imine, wich is reduced with the NaBH4/NiCl2 complex to the amine. Then filter, and do the usual workup.

It is a combination of the known Al/Hg/Nitro reduction with the above Article.

Would this work to give the secondary amine?
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solo
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[*] posted on 14-12-2006 at 11:13
Reference Information


Reduction Of Nitroalkanes to Amines Using Sodium Borohydride - Nickel(II)Chloride - Ultrasound
John O. Osby and Bruce Ganem
Tetrahedron Letters 26(52), 6413-6416 (1985)
HTML by Rhodium

Abstract
The combination of NaBH4 with catalytic quantities of NiCl2 smoothly reduces aliphatic nitro compounds to amines in methanol; Ni2B formed in situ is the active catalyst.

Excerp

......Here we report that the combination of nickel boride (Ni2B) and NaBH4 in CH3OH smoothly reduces a variety of primary, secondary and tertiary nitroaliphatic compounds to amines within ca.

[Edited on 14-12-2006 by solo]

Attachment: Reduction Of Aliphatic Nitro Compounds To Amines Using NaBH4.pdf (111kB)
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Drunkguy
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[*] posted on 15-12-2006 at 02:26


Ive read that NiCl2 is quite toxic.
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Waffles
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[*] posted on 16-12-2006 at 09:22


Quote:
Originally posted by Drunkguy
Ive read that NiCl2 is quite toxic.


It is toxic and potentially carcinogenic, but not excessively so (not more than many other transition metal salts). Just use normal precautions (gloves, ventilation).




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brainetix
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[*] posted on 16-12-2006 at 11:08


So you think this will work?? I found no reasons why not.

Could the NiCl2 replaced by NiSO4? Does anybody know the solubility of NiSO4 in MeOH?
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enima
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[*] posted on 16-12-2006 at 11:57


I'd dry up the methanol before proceeding with the reductive amination.
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jon
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[*] posted on 16-12-2006 at 12:01


why use nickel boride in a reductive amination in the first place?
plain NaBH4 is proven to work in many instances my question is what is the advantage?
The problem with NaBH4 in reductive aminations is simply reduction of ketone in equilibrum between shiff's base to an alcohol.
So to avoid this you can isolate the shiff's base by first preparing it and azetropically distilling of the water or you can dry it over silica.
alternately you can use sodium triacetoxy borohydride, or the cyanoborohydride, this has been discussed ad infinitum.

[Edited on 16-12-2006 by jon]
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haribo
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[*] posted on 16-12-2006 at 14:26


I've used tbe Zinc/Nickel couple to reduce oximes and it worked very nicely. DIBAL is a bit of a pain but yes, plain NaBH4 does work...
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jon
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[*] posted on 17-12-2006 at 00:20


oximes of the saturated oxime or the unsaturated oxime?
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haribo
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[*] posted on 17-12-2006 at 06:50


Errr... Could you repeat the question?
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jon
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[*] posted on 18-12-2006 at 22:54


oh I was thinking of the intermediate in the reduction of a nitroolefin.
so what you are talkin about is the oxime derived from condensation of ketone and hydroxylamine, so i awnsered my own question.
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[*] posted on 19-12-2006 at 04:51


Thank god for that, I thought one of us had gone mad and I was pretty sure it was me.
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