[Bakterien]

Got a quite old bottle of NaCNBH4, it has been stored in a cold dark room. How do I know that it's still ok to use? I have red that it quickly decomposes in contact with air.

[zsinger]

Be careful with reducing agents, as they can be explosive when in contact with air and water.  Try a reductive amination with it, as that is the reaction which it is most widely used for.  (I.E.will reduce imines, but NOT ketones).  The cyano group makes the reagent a smidgen less reactive by pulling electron density away from the "borohydride" part of the reagent, contributing to its reduced reactivity.  Im sorry if this was not the correct way to format the answer, although I am not sure how to answer this in the socratic method.
            Respectfully
                    -Zack

http://en.wikipedia.org/wiki/Sodium_cyanoborohydride

[Bakterien]

Thank you, I appreciate your answer. Another quesition, I should do my reaction in dry methanol. How do I dry it ? Destillation + molecular sive 3Å ?

[Benzene]

http://www.sigmaaldrich.com/MSDS/MSDS/DisplayMSDSPage.do?country=US&language=en&productNumber=156159&brand=ALDRICH&PageToGoToURL=http%3A%2F%2Fwww.sigmaaldrich.com%2Fcatalog%2Fproduct%2Faldrich%2F156159%3Flang%3Den

why are you choosing methanol as a solvent?

[zsinger]

Beauty of that reagent is it tolerates aqueous environments…...

[Benzene]

Beauty of that reagent is it tolerates aqueous environments…...

Wow! I did not know that, I just googled the reagent and I discovered this article: http://www.designer-drug.com/pte/12.162.180.114/dcd/pdf/sodium.cyanoborohydride.pdf

It says the reagent is stable in water even at pH 4!

[Mishifus]

Kinda off-topic, but if your cyanoborohydride ends up failing you, you can always easily prepare sodium triacetoxyborohydride (NaBH4 in glacial AcOH for some minutes), which, for reductive aminations, is just as good (if not better) than NaCNBH4, although it does react with water.

[zsinger]

Mishhifus,
I have never tried it that way?  What are the advantages to doing it this way?  I am a student of "don't fix what aint broken" .
                 -Zack

[Mishifus]

Hi Zack!

There is plenty of literature about STAB and its advantages. For starters, I'd recommend J. Org. Chem. 1996, 61, 3849-3862 . Not sure if I can quote directly (I am new here !) Some advantages include that the reagent is really easy to prepare (you can also prepare it in situ), it is much less toxic than NaBH3CN and doesn't produce toxic byproducts, and it is also faster, as far as I know. There's a comparison between these reducing agents in the aforementioned paper.

[kamiyu]

Hi all

1) I have used the NaCNBH3 for reductive methylation. The solvent is solely acetic acid. I think the reagent tolerates protic things.

2) I think sodium cyanoborohydride has the formula of NaCNBH3.

[spirochete]

Beauty of that reagent is it tolerates aqueous environments…...

Even NaBH4 can be put in methanol as a solvent, and of course NaBH4 is more reactive than NaBH3CN

[Bakterien]

Is there any danger with NaCNBH4 ? I am bit worried about the cyanide...

Should I do the reaction under inert atmosphere?

[kamiyu]

1) I do not think that kind of reagent is particularly toxic. I suggest you follow the protocol of your institution of disposing it. If there is none, then google it about disposal.

2) I think there is no need to use inert atmosphere. When I used this reagent for reductive methylation of amine in the past, I just mixed everything together and stir at rt. Good results.

[zsinger]

Stuff is great……just hard to find and usually quite expensive.  Can be made, but play with cyanide at your own risk!  Reductive aminations work great with the reagent with a variety of pHs in near quantitative yield.  Additionally, as mentioned, aqueous environment is no problem!  Really a great reductant for amines!!!!!
                 -Zack

[PhDoc]

Reductive aminations in the biopharmaceutical industry are done using sodium triacetoxyborohydride due to lower level of toxicity. As Mishifus indicated, this reagent is cheap and very easy to make.

When reducing imines, NaCNBH3 requires pH 2-4 in order to work since the key step is protonation of the imine, making the species electrophilic enough for the hydride reagent. The reaction is typically performed in methanol solvent. Although some people use dry methanol, it's never used on an industrial scale.

Likewise, on a kilogram scale dry methanol is not used for sodium triacetoxyborohydride. Once you try this reagent, you may never go back to NaCNBH3 unless you absolutely need it. In methanol, there is enough acetic acid liberated from the reagent to produce a pH 3 solution, hence there is no need for addition of acid.