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CuReUS
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Quote: Originally posted by Nicodem  | | alpha-resorcylic acid is commercially available and very cheap. I'm quite confident its reaction with excess n-BuLi in THF would give
1-(3,5-dihydroxyphenyl)pentan-1-one |
I might be missing something here,but from my searches,n-buLi with alpha resorcylic acid will give both the ketone and the tertiary alcohol.
http://pubs.acs.org/doi/abs/10.1021/jo00869a020
http://onlinelibrary.wiley.com/doi/10.1002/(SICI)1099-1395(1...
I think a better approach is to first convert alpha resorcylic acid to the nitrile and then react it with n-BuLi
[Edited on 22-10-2016 by CuReUS]
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Maroboduus
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Wouldn't using these various chloride Lewis acids to make allylbenzene give you a lot of phenyl 2-chloropropane?
Seems to me the reaction conditions would hydrohalogenate the allylbenzene quicker than you could say Markovnikov.
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CuReUS
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they will.
nicodem has already explained this in the previous pagehttp://www.sciencemadness.org/talk/viewthread.php?tid=9310&a...
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clearly_not_atara
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The arylzinc/allyl acetate method still seems attractive to me, even though acetonitrile is used as solvent. CoBr2/ZnBr2 are used to catalyze the
formation of the arylzinc compound from the aryl bromide. Attached.
I'm still not sure whether you can use allyl formate (which can be synthesized directly from glycerol) in place of allyl acetate. It would make things
quite a bit simpler.
Attachment: arylzincallylacetate.pdf (68kB)
This file has been downloaded 594 times
[Edited on 23-10-2016 by clearly_not_atara]
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Maroboduus
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I understand that the over alkylation he referred to would be from chloropropanes bonding with the benzene, but I was pointing out that the phenyl
2-chloropropane could also be a significant product itself. In fact, checking the literature I see that FeCl3 and allylchloride in benzene has been
used as a means to generate 2-chloropropane before, although the yield was mediocre, and over alkylation products were a large part of the impurities.
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Waffles SS
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All possible way for synthesis of Allylbenzene by reaxys
Attachment: Allylbenzene.pdf (1.8MB)
This file has been downloaded 1656 times
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Cryolite.
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I wonder why no one has brought up a route from cinnamaldehyde, since the OP mentioned it a a potential starting material. If cinnamaldehyde can be
reduced to 3-phenylpropanol, it can then be dehydrated to allylbenzene (and then isomerized to propenylbenzene)
However, this leaves the question of which reducing agent to use. I believe catalytic hydrogenation works, but can anyone think of an easily
accessible reducing agent which can effect the same transformation? Dithionite comes to mind as a possibility, since it can reduce conjugated ketones
at the double bond, but it can also reduce aldehydes to alcohols, which breaks conjugation (this second reaction would probably be favored, actually).
Maybe zinc or aluminum amalgam?
Edit: I believe the original Huang-Minlon paper on carbonyl reduction with hydrazine gives cinnamaldehyde to propenylbenzene as an example. However,
this requires handling hydrazine hydrate and working with sodium hydroxide in refluxing ethylene glycol.
[Edited on 25-10-2016 by Cryolite.]
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CuReUS
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| Quote: Originally posted by Cryolite. | | If cinnamaldehyde can be reduced to 3-phenylpropanol, it can then be dehydrated to allylbenzene (and then isomerized to propenylbenzene).However, this
leaves the question of which reducing agent to use.Can anyone think of an easily accessible reducing agent which can effect the same transformation?
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accessibility of reagents depends on where you live.Something easily accessible to one person might not be easily accessible to another
anyway,see the 4th post by syndenhams in this thread https://www.thevespiary.org/rhodium/Rhodium/Vespiary/talk/in...
he has suggested 8 different methods to get what you want.Take your pick 
| Quote: | | Maybe zinc or aluminum amalgam? |
clemmensen's reduction will give you phenylpropane,not phenylpropanol IMHO.I don't know about Al,but I am skeptical.Like atara says here http://www.sciencemadness.org/talk/viewthread.php?tid=6380&a...,"if it did,someone would have noticed"
| Quote: | | cinnamaldehyde to propenylbenzene... requires handling hydrazine hydrate and working with sodium hydroxide in refluxing ethylene glycol.
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not anymore,A better method has been found https://en.wikipedia.org/wiki/Wolff%E2%80%93Kishner_reductio...
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Cryolite.
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I was aware of the tosylhydrazone based reductions, but sodium cyanoborohydride is unobtanium for me (and for most people, I presume).
However, this paper http://pubs.acs.org/doi/abs/10.1021/jo01200a017 does give hope for a viable reduction: it achieves the desired reduction with nickel-aluminum
alloy in 50% yield. Thanks for the link.
Since I doubt the nickel is playing any role in the reduction other than as an electron shuttle, maybe a metal salt (like copper chloride) and
aluminum powder can be used for the reduction?
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clearly_not_atara
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On the one hand, it seems possible that some other reductants like dithionite (which IIRC does well in such 1,4-reductions) could work as well, but on
the other hand, I'm not sure that you can make p-toluenesulfonylhydrazine without going through hydrazine. It's cool if you can buy it, but unless
you're really interested in making propenylbenzene as opposed to using propenylbenzene, it's cheaper to buy the product, and if you are specifically
interested in making propenylbenzene it seems like cheating to buy something that's so much more sophisticated.
On the other hand, salt metathesis of a primary sulfenamide halide with an alkali metal cyanate might yield the sulfenylurea:
KNCO + PhSNH3Cl >> PhSNHCONH2
Oxidation of which gives the sulfonylurea:
PhSNHCONH2 + H2O2? >> PhSO2NHCONH2
And the Hoffmann rearrangement:
PhSO2NHCONH2 + Br2 >> PhSO2NHNH2
A primary sulfenamide is formed in situ from a thiol and an N-chloroimine (maybe TCCA, DCCA) to form a sulfenyl chloride and then bubbling ammonia
through the solution and used in situ, usually to react with carbonyls (another kind of electrophile) to make N-sulfanylimines:
https://books.google.com/books?id=JE6GAwAAQBAJ&pg=PA562&...
It looks like a one-pot reaction (albeit at -30C and hopefully there's a cyanate that dissolves in chloroform) from the thiol to the sulfenylurea,
amazingly.
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CuReUS
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http://onlinelibrary.wiley.com/doi/10.1002/jccs.200700220/fu...
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