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Author: Subject: Reduction of Nitro > Amine: Sodium Aluminum Hydride (NaAlH4)/Lithium Borohydride (LiBH4)?

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[*] posted on 14-1-2024 at 16:25
Reduction of Nitro > Amine: Sodium Aluminum Hydride (NaAlH4)/Lithium Borohydride (LiBH4)?

Hello all, first time poster, long time lurker, etc.,

I'm posting as I've managed to find myself on the endless rabbit hole of insanity inducing proportion for many users before me - that of access to hydride reagents.

Of course, there's tonnes of dissolving metal reactions which will reduce a nitro to an amine, but let's just pretend I'm a shill exclusively for hydrides which will accomplish this.

I'm aware that the usual choice is LiAlH4 or Red-Al/Vitride, however I was curious as to whether anyone had personal experience for proof/any literature showing that LiBH4 and/or NaAlH4 will reduce nitro groups to the amine? A preliminary Google Scholar search turned up empty, though I am new to this sort of thing.

Reason for these hydrides in particular is that I imagine they'll be more likely to arrive okay from overseas in comparison to a big fat "LiAlH4" sticker on the box.

Any help would be amazing, thanks so much!

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[*] posted on 14-1-2024 at 16:45

Hello and welcome, great to see another Australian on the forum!
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[*] posted on 15-1-2024 at 09:43

I found a paper on the reduction of nitro groups with sodium borohydride and copper sulfate...

Attachment: s-1990-21113.pdf (132kB)
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Lionel Spanner
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[*] posted on 15-1-2024 at 16:12

If you're reducing aromatic nitro compounds, using sodium dithionite is an easier and more practical method; metal hydrides tend to produce azo compounds instead.

If you're reducing aliphatic compounds, sodium/lithium borohydride are not effective on their own, and need to be combined with something like TMS chloride. Lithal tends to produce hydroxylamines and oximes as by-products.

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[*] posted on 15-1-2024 at 17:36

I have tried several reduction reactions of nitro compounds into amines with both LiAlH4 and NaBH4. The details on the specific compound are usually pretty important for the conditions if you want to achieve reasonable yields. NaBH4 on it's own isn't going to reduce a nitro group in most circumstances, but I have had very good success using either nickel or copper chloride along with NaBH4 to reduce compounds you would only expect LAH to work on. The mechanism is complex and not fully understood, but I think of it as the NaBH4 reducing the copper or nickel chloride into metal nanoparticles, which make the make the hydrogen more active.
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