I have a gemini quaternary ammonium salt that also contains two secondary amide groups, which I need to reduce to amines.
I tried using LiAlH4 in 6 eq. in anhydrous THF at 66 °C, but that degraded the entire molecule to pieces. The same happened when I lowered LiAlH4 to 2.5 eq. at RT in anhydrous THF. For workup I used 15% aquaous solution of NaOH and afterwards an extraction water/CHCl3.
You can try some borane reagents, depending on the structure of your compounds. These methods are often mild and chemoselective.
One example you have here: https://doi.org/10.1039/C4QO00317A.
Best of luck
Try reduction using silanes :
https://www.organic-chemistry.org/synthesis/C1H/reductionamides.shtm
I agree with Ivana and Jurgen, using milder reducing agents might be a good starting point.
An alternative would be to go via the imidate using Meerwein salts, and you can use both boranes and silanes for the reduction. It’s longer than a straight reduction, but the whole process is relatively mild:
e-EROS Encyclopedia of Reagents for Organic Synthesis (2008), 1-9
However, if you need to use aluminium based reducing reagent, there is a very easy work up process:
http://www.chem.rochester.edu/notvoodoo/pages/magic_formulas.php?page=aluminum_hydride_reduction
good luck
Dear Natalie Zivna thank you for sharing this very interesting technical question with the RG community. I agree with the previous expert answers in that borane or silane reducing agents are preferred in this case. As an inorganic chemist I'm not really an expert in organic synthesis. However, I assume that the problems here arise from the presence of the quaternary ammonium cations. I suspect that these can react with basic reducing agents such as LiAlH4 or NaBH4 in the sense of a Hoffmann elimination reaction. This will lead to a complete degradation of your starting molecule. Thus you should try neutral reducing agents such as BH3(THF) or (EtO)3SiH. The latter reagent is mentioned in the overview suggested by Jürgen Wintner. Please note that the compound is rather toxic and should be handled only in a well-ventilated fumehood.
Good luck with your research work and best wishes, Frank Edelmann
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