Author Topic: One more idea for LAHless nitrostyrene reductions  (Read 7939 times)

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Antoncho

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One more idea for LAHless nitrostyrene reductions
« on: September 07, 2000, 05:51:00 PM »
Does anyone know what happens if you reduce a nitrostyrene with a non-complex hydride, like, say, NaH? Maybe it can serve as a LAH substitute? Maybe, like in NaBH4 reductions, nitrostyrene/propene can be turned into nitropropane/ethane, and to the final amine via Clemmensen?
I mean, the major advantage of NaH is that it can be self-made, and in the place where I live metallic sodium costs about 150 times less than LAH.
Any information will be greatly appreciated since I just can't afford the damn stuff and I'm not alone at that I guess.


Rhodium

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Re: One more idea for LAHless nitrostyrene reductions
« Reply #1 on: September 08, 2000, 12:47:00 PM »
NaH is not a good reducing agent, it is mostly just a strong base.


http://rhodium.lycaeum.org


CHEM_GUY

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Re: One more idea for LAHless nitrostyrene reductions
« Reply #2 on: September 08, 2000, 07:32:00 PM »
You could try a real ghetto metal hydride:  Places sell Nickel Metal Hydride batteries, NiMH.  Add that to a solution of nitro-styrene...

Try electrochemical, or hydrogenation of metals.


Read my Disclaimer: 

http://cantsueme.homestead.com


halfapint

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Re: One more idea for LAHless nitrostyrene reductions
« Reply #3 on: September 10, 2000, 10:28:00 PM »
In an organic chem text a few years back, I read that sodium, aluminum and hydrogen would combine into sodium aluminum hydride "by direct union of the elements". This was a very casual, unreferenced sentence mentioning contemporary work. I would expect this synthesis to occur at elevated temperature, though that was not stated. For sure, NaAlH4 can bee directly substituted for LiAlH4 in any and every reduction, by adjustment of the quantity. If getting sodium is easy, you are the bee to give us the report on sodium aluminum hydride!


surroundsoundreverbfuzzbustersleagueresonancemodulation

hest

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Re: One more idea for LAHless nitrostyrene reductions
« Reply #4 on: September 11, 2000, 12:58:00 AM »
Sodium and hydrogen at app. 300°C gives NaH
NaH and AlCl3 (and a bit NaAlH4) gives NaAlH4
The first is hard to doo at home, the next i dificult.
NaH and AlCl3 is easye to get and a way to make the NaAlH4
LiH is also easye to get, someone use it as a solid source og H2 (24l in 7g)
But for small scale production, i do not think it is worth the troble.
And large scale prod. is easyer with H2 and presure

halfapint

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Re: One more idea for LAHless nitrostyrene reductions
« Reply #5 on: September 11, 2000, 08:42:00 PM »
Alas for the days of grammar and rhetoric!
Don't the schools teach Greek and Latin any more, deportment and oratory?

It's OK, hest, just wanting to poke fun at your spelling while I'm thanking you for the data.
"the next i dificult" just doesn't communicate to me; do you feel that reacting NaH with AlCl3 is or isn't difficult to do?
I might either agree or disagree with your opinion, if I knew what it was.
Did you imply that 24 liters of gaseous hydrogen can be produced by 7 grams of lithium hydride?
Let me encourage you to use more keystrokes.

Hey, I talk like this when I'm with my hog biker buddies. They dig.



surroundsoundreverbfuzzbustersleagueresonancemodulation

hest

  • Guest
Re: One more idea for LAHless nitrostyrene reductions
« Reply #6 on: September 11, 2000, 10:43:00 PM »
It's ok to make fun of us foreign people, we have a lot of humor. If you think my english is bad you should see my german and french.(but i'm caple of communicate on these language too)
Yes the mixing of NaH and AlCl3 is hard to doo, the reaction is dificult to start and takes some time. You end op with a thick solution and ewerye thing has to bee dry. I once thort( ups i mean thought) that LiH and AlH3(ups i mean AlCl3) was the way to cheap LiAlH4, but i ended up with bying it from Aldrich. And yes two mole of LiH gives one mole of H2 (Yea i know, 14g (not 7) LiH gives 24l H2)



KrZ

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Re: One more idea for LAHless nitrostyrene reductions
« Reply #7 on: September 12, 2000, 12:00:00 AM »
Nitrostyrenes are a big hassle. We NEED more cyanohydrin routes to PEAs, I demand references!  I've been looking myself but have yet to turn anything up :-(

Rhodium

  • Guest
Re: One more idea for LAHless nitrostyrene reductions
« Reply #8 on: September 12, 2000, 12:24:00 AM »
There is a US patent which reduces benzaldehyde cyanohydrins to phenethylamines with phosphorous pentasulfide, but I don't have its number handy. Perhaps it can be found using a patent search engine?


http://rhodium.lycaeum.org


KrZ

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Re: One more idea for LAHless nitrostyrene reductions
« Reply #9 on: September 12, 2000, 09:33:00 AM »
Thanks for the tip rhod. I will continue digging until something turns up.

halfapint

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Re: One more idea for LAHless nitrostyrene reductions
« Reply #10 on: September 12, 2000, 03:06:00 PM »
Excuse me, Hest. I was not aware English was not your first language. (Had you studied Greek, Latin, deportment and oratory for real, it would have helped in spelling several languages!)

You once thought (not thort) that LiH and AlCl3 was the way to cheap LiAlH4, I take it, not AlH3.

What solvent were you using to combine NaH and AlCl3, that got so thick? What temperature? Would a seed amount of NaAlH4 have made it start quicker?

Uh, cyano what?


surroundsoundreverbfuzzbustersleagueresonancemodulation

hest

  • Guest
Re: One more idea for LAHless nitrostyrene reductions
« Reply #11 on: September 12, 2000, 07:37:00 PM »
All forgiven halfapint, if I get the time I will take a class in latin ;-)
I used Ether and diglyme as solvent.
I did not heat it, but sometimes it did it by its self :-(
Yes adding some LiAlH4 would help (See H.I.Schlesinger Am.Soc.,69,1199,(1947))


halfapint

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Re: One more idea for LAHless nitrostyrene reductions
« Reply #12 on: September 13, 2000, 11:12:00 AM »
don't post sources


surroundsoundreverbfuzzbustersleagueresonancemodulation

Ritter

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Re: One more idea for LAHless nitrostyrene reductions
« Reply #13 on: September 13, 2000, 07:46:00 PM »
KrZ:
Here are two old refs on reducing mandelonitrile derivatives:

Benzoyl derivative:  J. Am. Chem. Soc., 50 3373 (1928)
O-carbethoxymandelonitrile derivative: Ann., 564 49 (1949)

KrZ, could you please post the ref you mentioned concerning the acetyl derivative of mandelonitrile?

Tks
Ritter

perpeetuum

  • Guest
Re: One more idea for LAHless nitrostyrene reductions
« Reply #14 on: May 24, 2001, 12:05:00 AM »
So here is 'quite possible' way to produce own (and relatively cheap) LiAlH4 from LiH and AlCl3 in (anhyd.)Ether as a solvent under good stirring ang temperature something above the room one (40-50 C degrees). Atmosphere could be the 'normal' air, but the reaction should take plenty of time, if it is really possible... :P
....I would accelarete it in MW (on very mild irradiation) a little--- this could help. But not above 70 C deg.

Greensnake

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Re: One more idea for LAHless nitrostyrene reductions
« Reply #15 on: May 24, 2001, 12:23:00 PM »
Hmmm, ain't Red-Al preparation from scratch kinda simpler than LAH, for all the same purposes?

perpeetuum

  • Guest
Re: One more idea for LAHless nitrostyrene reductions
« Reply #16 on: May 24, 2001, 08:38:00 PM »
maybe little simpler - and good for learning - and also via rP/HI you obtain also boranes, iodides and phosphines ---> that means hangovers  8)

but be quiet. the masters of chem-science are speaking. we are only aprentices, so rather listen and learn, so as me :)

smiley_boy

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Re: One more idea for LAHless nitrostyrene reductions
« Reply #17 on: May 25, 2001, 02:38:00 AM »
Antocho, zdravstvooytye, droog! G'de della?

So, you want to reduce nitrostyrenes, but you don't want to use LAH? I'm assuming you must not to want to use hydrogenation either, though when it comes to economies of scale, this method effectively reigns supreme.

I like your thinking. Yes, NaAlH4 will do the trick as others have pointed out, but then you have the problem of acquiring or producing that.

Alternatively, under aprotic conditions you can combine NaBH4 and add a little LiCl (or better yet LiBr) to obtain LiBH4 in situ - a much, much more powerful reducing agent.

Here's a quick, overly-simplified lesson on the chemistry of borohydrides and aluminum hydrides and their activity. When the metals complex with BH4- or AlH4-, the relative size of the metal atoms has a huge effect. For example, with Li+, the overlap of electron orbitals around the Li is much too small to really overlap much with BH4-, plus lithium is not so free-and-easy with giving up its elecxtrons like a cation is supposed to (at least compared to other metals.) The result: the borohydride is very reactive. LiBH4- readily reacts with water or simple alcohols, just like LiAlH4. LiBH4 can reduce nitro groups to amino groups.

If instead we complex BH4- with Na+, we have a much better match-up. Na+ has a much larger electron cloud, and is much more willing to give up its electrons. Hence, we have a much more stable complex, and NaBH4 is fairly stable  even in the presence of water or alcohols. It isn't going to be able to reduce a nitro group.

If we go further down the table of elements, we will have KBH4, a compound that is even more stable.

Incidentally, there's also the classic rocket fuel Aluminum borohydride ( Al(BH4)3 ) as well - made by reacting 1 AlCl3 with 3 NaBH4 under aprotic conditins, this is actually a distillable liquid, and is extremely pyrophoric. Now with three borohydrides all sharing one stingey, pitiful little metallic center, this one really has some reactivity. As far as nitrostyrene reduction goes, I'm sure it'll get the job done; just don't expose it to moist air, or BOOM!!

Now, back to your question: what other options are out there? Well, there's electrolytic reduction, there's Vitride in toluene, there's zinc amalgam in alcohol, and borane in THF or ether. Actually, for the price, there's also sodium amalgam - once the method of choice, now poo-pooed for a number of different reasons.

I hope this helps...

smiley_boy

  • Guest
Re: One more idea for LAHless nitrostyrene reductions
« Reply #18 on: May 25, 2001, 03:02:00 AM »
Actually, speaking of borane, that seems like a topic that hasn't been as well addressed as I feel it should. Now, correct me if I'm wrong, but borane*THF can be produced from sodium borohydride by partial decomposition with sufuric acid in THF:

2 NaBH4 + H2SO4 + 2 THF -> 2 BH3*THF + Na2SO4 + 2 H2

So why isn't this taken advantage of? The reduction of nitrostyrenes using borane-ether complexes is a well-established procedure in the literature, providing good yields  and remarkable chemoselectivity; for some arylethylamines, its the only practical route. So why aren't people experimenting with this around here? Am I forgetting something?

To make myself more clear, this is what I'm proposing: you can replace the LiAlH4 in your average nitrostyrene reduction procedure with NaBH4 and H2SO4! Safe, cheap, available. How's that for practical? Hopefully this generates some interest...

Osmium

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Re: One more idea for LAHless nitrostyrene reductions
« Reply #19 on: May 25, 2001, 12:02:00 PM »
As far as I know NaBH4 is pretty expensive in the former Soviet Union. Or so I've been told. Could it be that this substance wasn't produced industrially, while Li was? Would make sense, since Li is/was processed for nuclear weapons purposes, one of the isotopes is used for hydrogen bombs (lithium deuteride). I remember that a few years back many of the available Li compounds had a slightly different molar weight compared to the naturally occuring isotope mixture, becausepart of the isotope in question had been removed prior to conversion to other compounds.