tupence_hapeny
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Nitrostyrene to phenyl-nitro-propanol with formaldehyde
Nitroalkanes undergo an aldol condensation with aldehydes, this much is known...
So, I suggest that it may be possible to use this reaction (the Henry Rxn) to convert nitrostyrene to phenyl-nitropropanol, in precisely the same
manner as nitromethane can be converted to 2-Nitroethanol and nitroethane can be converted to 2-Nitropropanol. The mechanism is based upon the fact that when a nitroalkane (actually a nitroalkene - it is converted by the basic catalyst)
reacts with an aldehyde, the aldehyde carbon bonds with the carbon adjacent to the nitro-group - not the nitro-group - thereby lengthening the carbon
chain and forming a secondary nitroalcohol from the primary nitro-alkene that is x carbon(s) longer than the original compound. Such reactions use
basic catalysts (such as Mg:Al hydratalcites), tetraalkylammonium compounds, and dry even Al2O3.
Therefore, one could make the nitrostyrene in a known manner, using benzaldehyde (or your choice of substituted benzaldehyde) and nitromethane (rather widely available and also far more easily
made than nitroethane). Separate the product and then react with formaldehyde to form the phenyl-nitropropanol of your dreams.
The other salient fact is that this very procedure is being used to make similar molecules (1) (2) in almost total enantiomeric purity.
[Edited on 22-5-2007 by tupence_hapeny]
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jon
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very intersting approach!
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Nicodem
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You are confusing nitroalkEnes for nitroalkAnes.
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stoichiometric_steve
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The other salient fact is that this very procedure is being useless, unless it is desired to make hydrocinnamic alcohol derivatives.
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jon
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I just noticed that too on reading the articles sounded promising but when you dig deeper not really
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tupence_hapeny
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| Quote: | stoichiometric_steve
The other salient fact is that this very procedure is being useless, unless it is desired to make hydrocinnamic alcohol derivatives.
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The use of phenylacetaldehyde and nitromethane would produce hydrocinnamic acid derivatives, as the nitro-group would end up at the end of the
lengthened chain, by virtue of being attached to the methyl - which is attached to the phenethyl...
This is fucking hard to discuss without the structure....
(albeit the nitro-version of the amine) is the projected product. es, well said, it is a hydrocinnamyl derivative - then again so is phenyalaninol.
As to useless, I think maybe not as the p-methoxy version of the same is dehydrated in 87% yield using NaI/Zn in one pot (I suggest that the protection of the same is rendered otiose by virtue of the fact that NaI/Zn will not remove
the N from this compound, although it may reduce it).
Anyhow, when the carbon bearing the nitro-group is reacted with an aldehyde the carbon bonds with the new carbon - which new carbon-carbon bond
doesn't alter the position of the nitro-group vis-a-vis the original carbon
Ballini & Petrini, 'Recent Synthetic Developments in the Nitro to Carbonyl Conversion (Nef Rxn)' (2004) 60 Tetrahedron 1017
I particularly draw your attention to examples #102-3, 105-6 (p.1024) & 294-6 (p.1036), as these illustrate the principle to which I avert. Also
see schemes 6 & 7 here (Another article on the subject by Ballini, et al).
Also see the use of adducts of known chirality in order to make the chiral side chains referenced in my previous post. (1 & 2) I am suggesting
only that if formaldehdye (or paraformaldehyde) were used instead of glyxolic acid, that the side chain would be extremely useful for those here.
| Quote: | Nicodem
You are confusing nitroalkEnes for nitroalkAnes. |
Yeah, but perhaps not for the reason you may think... See the first article I provide up there (also the second). The basic reaction scheme (I think
it is scheme 1 in both: [1] (nitroalkane + base = [2] nitroalkene + alkylhalide [3] / aldehyde [4] / or electron withdrawing group (EWG) [5] =
Secondary nitroalcohol). However, on closer inspection, the double bond (as illustrated) is probably not an olefinic double bond at all, in which case
it may be necessary to affect a reduction of the nitroalkene ((nitrostyrene) to phenyl-2-nitroethane prior to reacting it with either formaldehdye or
whatever. This can be achieved, although higher yields must be available.
tup
[Edited on 22-5-2007 by tupence_hapeny]
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jon
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it seems like your working harder just to avoid working hard.
sure nitroethane is a pain but so is that.
[Edited on 22-5-2007 by jon]
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tupence_hapeny
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Well, having gone down this track I find out that 2-nitroethanol is condensed with benzaldehyde to make PPA (Phenylpropanolamine), which given that it is (for all intents and purposes) a pseudo/ephedrine derivative can be transformed directly to P2P with
sulfuric acid & ZnCl:
As I cannot get DMF at the present time, I feel fairly certain that neither can others... Therefore, my capacity to prepare nitroethane, even if I
wanted to, is fairly circumscribed. The fact that a route exists that would allow such chemically challenged individuals to reach their supposedly
unreachable goals would suggest that the current chemical bans are somewhat redundant...
BTW Here is another example of what I was trying to get across.
tup
[Edited on 22-5-2007 by tupence_hapeny]
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jon
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I concluded that the sn2 reaction was the only feasible route to nitroethane the other methods are'nt as straight forward and have low yeilds and the
nitrite ester codistills which could be an explosion hazard although i have'nt verified it.
since DMF is restricted and there aren't any other polar solvents it would work in I see your point.
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stoichiometric_steve
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| Quote: | | Originally posted by tupence_hapeny 2-nitroethanol is condensed with benzaldehyde to make PPA (Phenylpropanolamine) |
bullshit.
look at the structures... benzaldehyde + nitroethanol gives you, in the best case, 3-phenyl-2-nitropropanol. which is NOT the PPA you refer to.
what are you after, anyways? get some fucking nitroethane and stop messing things up.
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tupence_hapeny
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The rather pretty reaction scheme (in the first of the links, so kindly reproduced by your good self, you will see that they provide the reaction
schematic for you) says otherwise, and logically it should work (unfortunately, I was unable to prove that before).
Of course, they do reduce the nitro-group to the amine, but I made no mention of this point, I rather thought that would be taken as read?
tup
PS Jon, FYI instead of the the rather involved distillation of the end product from this synthesis (including a rather odd chemical as a codistillate)
I found this on the properties of 2-nitroethanol:
http://cameochemicals.noaa.gov/chemical/20770#section4
Would you believe that unlike both methanol and nitromethane (and paraformaldehyde if there is any left) 2-nitroethanol is virtually insoluble in
water (1mg/mL @ 70C). I've heard that sometimes chemicals can be separated by virtue of their varying solubilities in certain solvents
[Edited on 23-5-2007 by tupence_hapeny]
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jon
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yeah i was thinking about the ppa scheme too and it would yeild a 1,3 diol compound the scheme i think is wrong and misleading.
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stoichiometric_steve
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| Quote: | Originally posted by tupence_hapeny
The rather pretty reaction scheme (in the first of the links, so kindly reproduced by your good self, you will see that they provide the reaction
schematic for you) says otherwise, and logically it should work (unfortunately, I was unable to prove that before). |
you have to learn to read equations and integrate the logic of reaction mechanisms into that...
one hint: the alpha carbon of nitroalkanes bears an acidic proton, and only that one. no chance the carbinol hydrogen will EVER be acidic in this
situation. and now go and see that all you have posted is based on the misunderstood theory of the henry reaction...sorry for you
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tupence_hapeny
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| Quote: | | one hint: the alpha carbon of nitroalkanes bears an acidic proton, and only that one. no chance the carbinol hydrogen will EVER be acidic in this
situation. and now go and see that all you have posted is based on the misunderstood theory of the henry reaction...sorry for you
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OK
So your statement is (from my limited understanding) that without an acidic carbon (such as the one adorning 'some' (primary) nitroalkanes, the
nitroaldol (Henry) reaction will not work?
I admit it, I might be wrong, however, I suggest you should inform these people that what they have written is a load of codswallop:
http://www.organic-chemistry.org/namedreactions/henry-reacti...
http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/2004/126/i16...
http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=v78...
http://www.arkat-usa.org/?VIEW=MANUSCRIPT&MSID=1589
Although on the basis of the last one, this compound may be the result (although, while working with a nitro-group this is less of an issue than it
would be with an amine)
http://www.erowid.org/archive/rhodium/chemistry/amph.phenylp...
Simply because concentrated H2SO4 also acts as a dehydrating agent, which is why I believe it works in the conversion of PPA to P2P?
Anyhow, if the reaction conditions are kept as per the ones cited here:
http://www.iptonline.com/articles/public/IPTFOUR79NP.pdf
I believe that what is sought could be the result.
tup
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stoichiometric_steve
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sorry man. you obviously dont know what "henry reaction" means.
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Nicodem
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The most confused and absentminded person I ever had the privilege to know, in both virtual and real world! You leave me no choice but to admire your
incredible skills.
Tup, like I already told you, stay the hell away from the primary chemistry literature and get yourself a book about basic organic chemistry. The
primary literature is not appropriate for any beginner let alone someone so confused. Trust me, it can only do you more harm!
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stoichiometric_steve
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could this thread kindly be deleted.
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