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Category: Synthesis
Posted on: May 15, 2007 8:58 PM, by Molecule of the Day
Here is a quickie: sodium triacetoxyborohydride.
Most people use sodium cyanoborohydride as their mild reducing agent in reductive aminations. Triacetoxyborohydride works just fine and has the added advantages of not stinking and not being quite so poisonous. Sodium triacetoxyborohydride: now without cyanide!
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Comments
Almost everything about organic chemistry has been declared in heinous violation of the EPA, DoEducation, and Homeland Severity. Has the alphabet soup of Washington incompetence now stolen the very fragrance of our endeavors?
Once one has done isonitriles by the decigram, everything else is a pale imitation of scent.
Posted by: Uncle Al | May 16, 2007 12:31 AM
For a good review of this reagent's utility check out this JOC article...
DOI: 10.1021/jo960057x
Posted by: VTChris | May 16, 2007 11:06 AM
I once used Sodium Cyanoborohydride in my final year as an undergrad, the work up was a right pain in the arse. I was doing it on quite a large scale, so it took a long time to neutralise and I seem to remember it taking about a litre and a half of DCM to extract the product. When took the solution out from the fume hood I realised pretty quickly that I hadn't completely neutralised the solution. To this day the smell of almonds still makes me uneasy, even if it's just shower gel!
I've used Sodium TAB a few times as well, it was on a much lower scale but it seemed easier to deal with and I guess not giving off cyanide is always a plus.
Posted by: Mike | May 16, 2007 7:14 PM
One thing that triacetoxyborohydride will not do that cyanoborohydride will do is reduce oximes to hydroxylamines. Not sure why, but cyanoborohydride appears to be about the only reagent to do this - almost anything else over-reduces to the amine. As a result I spent 3 years using this reagent - never smelt almonds once...
Posted by: Steve | May 29, 2007 8:02 AM
Another case of noses and smell being highly personal. I HATE the smell of STAB. Not as much as i hate that of NaCN(BH4) but i still loathe weighing it out.
Of course, i think nBuOH smells nice, so you know my opinion is suspect :D
Posted by: Yttrai | June 8, 2007 9:43 AM
"One thing that triacetoxyborohydride will not do that cyanoborohydride will do is reduce oximes to hydroxylamines. Not sure why, but cyanoborohydride appears to be about the only reagent to do this - almost anything else over-reduces to the amine. As a result I spent 3 years using this reagent - never smelt almonds once..."
Borane-pyridine complex in mild acidic conditions does it just as well (I've done it repeatedly and observed no over-reduction). But then, it's probably more expensive.
Posted by: Fran�oisG | July 5, 2007 3:08 AM