Dimitri
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NaBH4/H4BK
Looking at the two they seem to have the same uses, the only trouble I have is whether the potassium borohydride is able to be converted into
Potassium Triacetoxyborohydride following the same procedure used for the NaBH4?
I am basically after NaBH4 to convert into triacetoxyborohydride but am unable to get it, but am able to get Potassium Borohydride.
Any info on this would be much appreciated..
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Klute
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You would need to check the respective solubilities. IIRC, triacetoxyborohydride forms a thick suspenion/gel when made from NaBH4, as described by
Grind in the recent triacetoxyborohydride thread. So if the k salt is even less soluble, you might need to take appropriate precautions to avoid
excessive precipitation.
Otherwise, i think the reactivity of the two are rather similar, more so than the Li salt.
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jon
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kbh4 is easier to explain too it's used in water treatment.
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grind
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| Quote: | Originally posted by Klute
You would need to check the respective solubilities. IIRC, triacetoxyborohydride forms a thick suspenion/gel when made from NaBH4, as described by
Grind in the recent triacetoxyborohydride thread. So if the k salt is even less soluble, you might need to take appropriate precautions to avoid
excessive precipitation. |
I think NaBH(AcO)3 is nearly insoluble in toluene. KBH4 is generally less soluble in organic solvents than NaBH4. So I guess KBH(AcO)3 is completely
insoluble in toluene.
An excessive precipitation is not avoidable, at least in toluene. But that is no problem cause the reaction occurs even heterogeneously with high
yields.
KBH(AcO)3 is probably slightly less reactive compared with NaBH(AcO)3 and longer reaction times may be necessary.
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Dimitri
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Anyone heard of K borohydride being used in reductive amination? The other option is for me to make Sodium Borohydride as sodium hydride is availble
to me. Its just making the Trimethyl borate to react with it.
[Edited on 7-4-2008 by Dimitri]
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grind
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| Quote: | Originally posted by Dimitri
Anyone heard of K borohydride being used in reductive amination? |
Never heard but it should be possible. You can reduce a preformed imine with KBH4.
For reductive amination KBH(AcO)3 will be better. One can expect that all potassium borohydride compounds (KBH4, KBH3CN, KBH(AcO)3) are less soluble
in organic solvents than the comparable NaBH4 compounds.
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Klute
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Couldn't you possibly form TBA.BH4 (tetrabutylammonium borohydride) or even LiBH4 by metathesis? The TBA.BH4 is very soluble in DCM and other
chlorinated solvants IIRC, you would need to find a solvant in which KBH4 is soluble enough to be able to perform the metathesis though. I'm not sure
if the LiBH4 could done as easily though...
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grind
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http://www.rohmhaas.com/assets/attachments/business/process_...
Good review concerning sodium borohydride. The table (site 4) gives a comparison with KBH4 (and AcOH).
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Klute
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Apparently, LiBH4, very soluble in ethers, can easily be made from KBH4 and LiCl by metathesis according to this article.
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solo
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Direct and indirect reductive amination of aldehydes and ketones with solid acid-activated sodium borohydride under solvent-free
conditions
Byung Tae Cho, Sang Kyu Kang
Tetrahedron Volume 61, Issue 24, 13 June 2005, Pages 5725-5734
Abstract
A simple and convenient procedure for reductive amination of aldehydes and ketones using sodium borohydride activated by boric acid, p-toluenesulfonic
acid monohydrate or benzoic acid as reducing agent under solvent-free conditions is described.
[Edited on 10-1-2009 by solo]
Attachment: Direct and indirect reductive amination of aldehydes and ketones with solid acid-activated sodium borohydride under solv (307kB)
This file has been downloaded 3854 times
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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