ORGLIST: Reductive amination with NaCNBH3

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From: Paul D. Jones (pdjones$##$ucdavis.edu)
Date: Tue Dec 14 2004 - 12:50:16 EST


Will, at sufficiently low pH, you will most likely liberate HCN. However,
since you are working with acetic acid, which is a weak acid (and necessary
for the reaction), you should be fine. Of course, this absolutely must be
performed in a fume hood (as should all reactions).

I routinely use HCN and KCN to make a wide variety of molecules, usually
from 50-500 mmol in scale. As long as you are careful and use the proper
precautions (fume hood, proper waste handling), you will be fine.

If you are still unsure, you can use Na(OAC)3BH as the reducing agent.

-Paul

>Hi there
>
>I am wanting to reductively aminate a fluorophore into the reducing end of
>an oligosaccharide for subsequent reactions.
>
>I have dug up loads of stuff on this and they have all said pretty much the
>same thing
>
>Dissolve fluorophore in 0.15M AcOH/H2O (3:17 v/v), add to oligosaccharide.
>Add NaCNBH3 (1.0M in DMSO)
>Incubate for 16 hours at 37 degC
>I was planning on testing for the lack of reducing end of the
>oligosaccharide by whether Cu(II) is reduced to Cu(I), which I have used
>before for presence of reducing end of oligosaccharides.
>
>My question is to anyone who has worked with NaCNBH3.
>
>Can you work below pH7 with it or will it give off HCN? The reason I ask is
>I know that NaBH4 gives off H2 below pH7 when Ive used it for other
>reduction reactions.
>
>Ideal conditions quoted appear to be pH2.3 ish. Can someone promise me no
>HCN is going to be given off!!???
>
>Cheers
>
>Will

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