Sciencemadness Discussion Board - Synthesis of Allylbenzene

Synthesis of Allylbenzene

MEXCHEM2006 - 17-10-2007 at 18:01

Im looking for a suitable synthesis for allylbenzene , I found several synthesis but all have several drawbacks (expensive , rare reagents etc) , and I dont like friedel crafts alkylations

Cinnamyl alcohol reduction with HI doesn't work
http://content.arkat-usa.org/ARKIVOC/JOURNAL_CONTENT/manuscr...

Reduction with zinc dust uses too much solvent
http://designer-drugs.com/pte/12.162.180.114/dcd/chemistry/c...

I have access to Cinnamaldehyde and Cinnamyl alcohol and all the common reagents.

Any suggestions are welcome

chemrox - 17-10-2007 at 21:15

Quote:

I dont like friedel crafts alkylations

Friedel Krafts?

It's like saying you want to make alcohol but don't like fermentation.

I appreciate the paper and the old thread. What I don't understand is why you think the old thread didn't have enough possible approaches for you.. ithe thread seemed loaded with ideas to me and it's not a very interesting problem as things around here go.

Finally, it looks a lot like an amphetamine precursor ... boring!

[Edited on 17-10-2007 by chemrox]

Sergei_Eisenstein - 18-10-2007 at 00:29

It is possible to prepare allylbenzene via a Grignard reaction: bromobenzene, Mg and allylbromide. Suitable?

[Edited on 18-10-2007 by Sergei_Eisenstein]

Reference Information

solo - 18-10-2007 at 03:18

CATALYTIC SYNTHESIS OF ALLYLAROMATIC HYDROCARBONS
N. I. Shuikin and N. A. Pozdnyak
Russian Chemical BulletinVolume 14, Number 2,329-331, 1965

Summary
1. A simple method was developed for obtaining allylaromatic hydrocarbons by the alkenylation of benzene, toluene and tetralin with ally1 alcohol in the presence of zinc chloride. The yields were respectively 50.0, 72.9, and 60.0% of theory, when based on ally1 alcohol

2. Allyltetralin and allyltoluene are easily copolymerized with butadiene, forming elastomers.

[Edited on 18-10-2007 by solo]

[Edited on 18-10-2007 by solo]

Attachment: CATALYTIC__SYNTHESIS__OF__ALLYLAROMATIC__HYDROCARBONS__.pdf (193kB)
This file has been downloaded 3578 times

maniacscientist - 18-10-2007 at 09:36

I´ve been reading of a Grignard-like reaction with FeAcAc as a metallo organic catalyst that would yield allyl and even phenylacetone with this reaction. Never tried it though it´s on my list for the next 3-4 years.

Nicodem - 18-10-2007 at 10:24

I guess you are talking about the newest C-C coupling reaction involving Grignard reagents (Angewandte Chemie International Edition, 46, 4364–4366; attached bellow). It is an interesting reaction since before it was not possible to couple aryl grignards with alkyl halides with Pd and Ni catalysts generally used in the usual Kumada coupling (that is aryl halide + alkyl grignard) due to the dreaded alpha-hydride elimination. Apparently the Fe(acac)<sub>3</sub> causes no such side reaction while still being able to catalyze the Kumada coupling. That alone is reason enough for it being published in Angewandte.
Anyway, again you did not read the thread or else you would have noticed that Sergei already explained that phenyl grignard can be coupled with allyl halides. This is due to allyl (and also benzyl) halides not having eliminable hydrogens while being much more electrophilic than alkyl halides at the same time. Therefore they need no catalyst whatsoever to couple with Grignard reagents.

Attachment: Iron-Catalyzed Alkylations of Aromatic Grignard Reagents.pdf (115kB)
This file has been downloaded 2503 times

maniacscientist - 18-10-2007 at 10:54

I did read it and I know about the coupling of grignard with allylbromide/iodide, I just wanted to add to therudiemental works like Friedel Crafts and alkyl or allyl grignard, as these are the known methods.

Why´re you attacking me, I thought this forum were more gentle on beginners, yet you´re not very gentle and criticism might curb an intersting discussion, when there seems to be more interest behind as "just cooking" a drug precursor", which, I must admit, might not be the case here for most of the members around but to some it is; also, with shutinng-up an intersted in chemstry you might force him to not look at other promising parts of chemstry, because he feels to be left alone and just commences "cooking".

Nicodem - 18-10-2007 at 11:32

I would not consider my behavior as attacking you. It is more like attacking a certain kind of behavior and mentality. I consider this as some kind of accelerated learning and adaptation. You might have not noticed it, but in a couple of hours you managed to completely alter the way you post. Now you actually take care in writing comprehensible posts, spell check and verify before pressing the post button. And I'm sure you will also soon take care to read the threads before posting and avoid further off topic posts. The quality of your posts has improved immensely which is all I wanted.
Now I can finally welcome you here: Welcome!

maniacscientist - 18-10-2007 at 11:37

Thanks a lot... I realized this and now give me a rest *lol*

[Edited on 18-10-2007 by maniacscientist]

MEXCHEM2006 - 18-10-2007 at 15:07

I dont find suitable a Grignard reaction because magnesium metal is forbidden in my country , you need a special permission from the Army to buy it .

chemrox - 18-10-2007 at 19:03

Don't we all love governments? (Without them there'd be no wars.)

Anyway, can't you grind up automobile wheels?

Question: are Mg alloys used in automotive applications high enough in Mg to use for the Grignard? I think I've read about using such but might have been from not so reliable sources ... Rhodium par exemple ...

MEXCHEM2006 - 18-10-2007 at 20:20

I already tried using Mg alloys from wheels in a synthesis of alarm pheromone 4-methyl-3-heptanol (with bad results).

chemrox - 20-10-2007 at 12:00

try a simple one like Ph-Mg-Br-etherate. It's the easiest Grignard to make I know of. I had a job once making the shit by the carload for a ChemE/inventor. (He paid me to distill his ether too but that's another story)

Fleaker - 20-10-2007 at 12:44

Magnesium from alloy wheels is nowhere near good enough for a Gringard. I have pure magnesium turnings, and ingot, but given what it's going to...
BTW, there is an efficient pyrolytic way to allybenzene.

JohnWW - 23-10-2007 at 10:08

Mg from old Mg alloy car wheels ('mags") are, in fact, Mg-Al-Si alloys, possibly with traces of other elements. The Al in particular is likely to interfere with many reactions of Mg metal.

chemrox - 23-10-2007 at 20:24

Any chance of turning (couldn't resist) up a Cu-Mg alloy? These can enhance the yield. I agree that Al would be a poison and I didn't know, but should have expected, that to be a good percentage of wheel alloy. Please disregard the suggestion. Where would a Mg-Cu alloy be used in industry?

vulture - 24-10-2007 at 01:26

You don't want copper in your grignard reagents because you'll be making copper organometalics.

Antwain - 24-10-2007 at 02:17

copper oraganometalics have their uses, basically a less potent form of grignard, to put it simply. But if you want a grignad reaction then you dont want copper.

vulture - 24-10-2007 at 07:37

Copper organometalics are only useful if you want 1,4-conjugate addition instead of 1,2-addition. Which is not the case here. Their reactivity and basicity is also lower.

Nicodem - 25-10-2007 at 09:45

The chemistry of alloys has little to do with the chemistry of the metals from which it is composed. It is absurd to think that any magnesium alloy can be used to prepare Grignard reagents. Not to even consider that any alloy containing magnesium made for common use will be such as not to be prone to corrosion, oxidation, dissolution, etc. – thus also inert to alkyl and aryl halides.

MEXCHEM2006 - 25-10-2007 at 19:47

Reduction of cinnamaldehyde to cinnamyl alcohol with LiAlH4
http://www.ch.ic.ac.uk/local/organic/0405Expt5.pdf

Synthesis of allylbenzenes by cross-coupling of allyl bromide with arylboronic acids using a palladium chloride and tetraphenylphosphonium bromide intercalated clay catalyst
http://www.rsc.org/ej/GC/1999/a905846j.pdf

[Edited on 26-10-2007 by MEXCHEM2006]

trilobite - 26-10-2007 at 07:09

Quote:

Originally posted by vulture
Copper organometalics are only useful if you want 1,4-conjugate addition instead of 1,2-addition. Which is not the case here. Their reactivity and basicity is also lower.

Actually allylic couplings is one of the traditional uses for copper organometallics. In these cases copper salts such as CuI, CuCl*2LiCl, CuCN*2LiCl etc. are typically used in catalytic amounts. For example the Rhodium archive contains a preparation of safrole from catechol by Psychochemist (who obviously knew his shit) that employs CuI as a catalyst in this sort of reaction.

However it is my understanding that one of the problems is decomposition of the organometallic with liberation of copper metal which is able to catalyze the same decomposition. Optimal temperature depends on the reactants and employed copper species. Lithium salts are added to make copper more soluble in ethers. It appears that soluble salts of stoichiometry CuCN*2LiCl would give reasonably stable organometallics. This is the main reason I would feel uncomfortable with a magnesium alloy containing copper.

I'm also pretty certain that this question has been researched. Trying out different metal salts in Grignard reactions originates from the fact that in the beginning of 20th century magnesium metal had various impurities depending on the location, so the Europeans got different results compared to the Americans. The subject is discussed in Grignard Reactions of Nonmetallic Substances by M. S. Kharash and O. Reinmuth, published by Prentice Hall in New York year 1954. That is the book where I would look for answers on different alloys, but not on the modern organocopper chemistry.

-TheMadMen- - 29-5-2009 at 08:35

Hey man you'd be pretty dumb not to make allylbenzene by friedel-crafts, infact there is no excuse, what could be more simple, economical, cheap, infamous, and ( socially speaking ) dangerous than such a simple little benzene-Allyl alchohol conversion procedure? Heh. Allylbenzene synthesis is easy.

phenol derivitives

pip - 1-6-2009 at 09:30

Which alkylation would be best to apply to resorcinol instead of regular benzene? Shorter chain olivetol's are what i'm curious about. I have found a lot of literature about alkylating benzene derivitives however 5-alkylating resorcinol isn't mentioned in anything I have found only 4 alkylation unless it is about olivetol itself or the analogs for thc synthesis which have longer side chains than i'm interested in. Also i'm hoping that the olivetol synthesis I have found are more complex than nessesary because of the longer side chain or to increase yeild either of which isn't important to me.

Or am I just barking up the wrong tree trying to directly 5-alkylate resorcinol or Phloroglucinol (1,3,5 trihydroxybenzene)

Arrhenius - 1-6-2009 at 18:47

pip: Resorcinol (3-hydroxyphenol) is not going to get you to olivetol. If you try to alkylate that ring , you're going to end up with a mess, and none of the 5-alkyl product you want. Do also keep in mind that chain homologation of THC analogues has already been done...

Friedel-Crafts won't work well on phenols, as O-alkylation is a competing reaction.

-TheMadMen-: Friedel-Crafts reaction is really not that glorious. The 'atom economy' of the reaction is pretty awful considering it takes a mole equivalent of Lewis acid. Palladium chemistry is probably a better option.

I presume the desire to make allyl benzene is to access a renowned illicit substance. In that regard 1-phenyl-2-propene is a more easily had product.

pip - 2-6-2009 at 21:07

I don't understand by what you mean by chain homologation extending the chain on thc? I'm really not after thc so discussing how to take it and extend/shorten the chain to make an analog isn't an subject I am trying to touch on.

Just so I don't get flamed I am talking about an ethyl or n-propyl resorcinol while olivetol is n-amyl and supposed to be the shortest chain possible for an thc analog to have activity.

Arrhenius - 2-6-2009 at 22:04

I'm not trying to flame you, but having thought about THC analogues a bit myself, I figured that's probably why you're interested in olivetol & friends. Anyhow, like I said, resorcinol is unfortunately not a good starting point for these materials. Realistically, you would want to start with something like m-dinitrobenzene or m-dichlorobenzene, which will give you the correct electronic effects to get the alkyl group in the correct position. Still, by this route I think you'll find the Friedel-Crafts reaction a substantial hurdle.

pip - 2-6-2009 at 23:19

I just found this and it's for what i want but not thc however the patent imply's that increasing pressure to favor alkylation instead of dealkylation would help solve the problems of using the longer chain alcohol's

Attachment: Process_for_producing_mono_substituted_Resorcinol.pdf (134kB)
This file has been downloaded 2032 times

since I answered my own question I apologize for taking the thread off topic.

[Edited on 3-6-2009 by pip]

Arrhenius - 2-6-2009 at 23:49

Doesn't sound too promising as a laboratory prep reaction. Vapor phase 350-415C to get a mixture of 2, 4 and 5-Me/Et/Pr resorcinols. Yikes.

pip - 3-6-2009 at 00:04

Um you don't add all three alcohol's only the one you want to react. It can be methanol ethanol or propanol and the vacuum distillation/ fractional crystalation purifies it. And the min reaction temp is 276c not 350 to 400

Building an reaction vessle from scratch is less daunting than all the protection/deprotection involved with the classic ways not the mention all the conversions to get the product. Isn't the classic olivetol synth. like 7 or 8 steps?

Besides what's really needed as an reaction vessle why can't an glass vessle be filled with the right amount of reaction mixture so when the vessle is evacuated and sealed all the mixture can be heated to vapor phase while creating only enough pressure to satisfy patent requirements? I understand that might limit scale but hey it wouldn't take longer overall than the other ways.

[Edited on 3-6-2009 by pip]

BabyBird - 5-6-2009 at 00:57

apologies if this is taking this thread further off topic,

you are going to struggle to get friedel-crafts on a phenol to give a meta substituted product. it just won't do it, unless you are willing to make ortho para and then rearrange with HF at high temps to the more thermodynamically stable meta substituted material.
friedel crafts alkylation of phenols using alcohols or alkenes and a strong acid gives primarily mono alkylated material, indeed this is the commercial way of making nonyl phenols and a raft of other alkyl phenols. para can be selected for over ortho using zeolites.
O-alkylation is not usually a problem because under the influence of strong acid the O alkylated material will re-arrange to the c-alkylated material.

so if you have a way to meta alkylate a benzene ring with a very strong activating ortho para directing group such as phenol you are much cleverer than me.

similarly if you can F-C alkylate a benzene ring with meta directing groups like nitro or similar or worse 2 meta directing groups in anything like decent yield you are again much cleverer than me. it is going to require high temps and tough conditions if it works at all, but at high temps the alkyl cation is going to rearrange to the more stable secondary or tertiary cation, giving branched chain f-c products.

from memory the large scale olivetol syntheses used in the past used dihydro resorcinol monoethyl ether and a suitable alkyl organometallic adding 1 4 and then aromatize the product to the olivetol or meta subd phenol. this only works with straight alkyls.

[Edited on 5-6-2009 by BabyBird]

pip - 5-6-2009 at 06:31

The patent isn't an freidels-craft reaction as there is no halide and I might be wrong but I don't think titanium dioxide is an lewis acid . Babybird do you see a reason why the patent maybe bunk? Also mods maybe this should be split into an new thread?

Nicodem - 5-6-2009 at 11:40

Reactions do not get classified due to the reagents used, but due to the mechanism of the reaction. Thus a Friedel-Crafts alkylation needs not to involve alkyl halides (see http://en.wikipedia.org/wiki/Friedel-Crafts_reaction for examples or other precursors to the reaction electrophile). In fact, I think the most common reagents used in industry to form the electrophiles for the FC alkylation are alkenes rather than alkyl halides. If the reaction involves an alkylation at the aromatic ring and the carbocentered electrophile is created by acid catalysis (either from an alcohol, alkene, alkyl halide, ketone/aldehyde, or other) the reaction is a Friedel-Crafts alkylation, because unless a different mechanism is proven, an electrophilic aromatic substitution mechanism is assumed. Titanium dioxide, at least some of its forms, is an acid, though not TiO2 itself, but its surface is acidic. Similarly like silica, some forms of alumina and some zeolites.
BabyBird is right about the limitations in using FC reactions to obtain the thermodinamic product. In FC alkylations it is generally very difficult to obtain the thermodynamic product (=the product at which the rate of the retro-Friedel-Crafts reaction is the slowest). With alkyls such as t-butyl, benzyl and related this is not so difficult and can be done at "normal" temperatures with "normal" acids, but with less transferable alkyls (like the methyl or ethyl) the conditions needed can be really extreme. The method of the US4086281 patent posted above is most unlikely to be of any use for the synthesis of olivetol, or even 5-propylresorcinol, because you can not introduce n-alkyl groups via a Friedel-Crafts reaction. 1,2-Hydride shifts in carbocations are considerably faster than the rate of FC reactions, thus that patent method should give 5-isopropylresorcinol regardless if you use isopropanol or n-propanol.

Besides, 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 (at least three equivalents of BuLi are needed since two are lost at the phenolic groups). 1-(3,5-Dihydroxyphenyl)pentan-1-one can be reduced to olivetol by various means (hydrogenation over Pd-C would be the simplest method, or else reduction with silanes, but Clemenssen or Wolff-Kishner reductions could work as well). Since alpha-resorcylic acid, BuLi and Pd-C are all commercially available and relatively cheap, this might be the cheapest two step synthesis of olivetol possible. Of course, to see how possible this is one should first check the literature, but I leave that to those who are interested and not too lazy.

pip - 5-6-2009 at 19:07

Again olivetol is not the goal so the patent will work fine for the ethyl group I want. Thank you Nicodem I found that very informative, I had forgotten that it is more than just the halides that classify as an F/C reaction.

-TheMadMen- - 11-6-2009 at 00:02

Quote:

-TheMadMen-: Friedel-Crafts reaction is really not that glorious. The 'atom economy' of the reaction is pretty awful considering it takes a mole equivalent of Lewis acid. Palladium chemistry is probably a better option.

I presume the desire to make allyl benzene is to access a renowned illicit substance. In that regard 1-phenyl-2-propene is a more easily had product.

No no, i do not engage in the chemistry that i was recommending for this particular post. However, I believe allylbenzene is actually an illicit precursor in itself yes?? In so being, it is illegal to possess without a license, in which case, 1-phenyl-2-propene, or allylbenzene, is irrelevant really. But as to the atom economy aspect, you are correct indeed, it is a very inefficient reaction from a statistical point of view, but it's not as if the benzene is destroyed, it just remains unreacted, so it can be fed back into the process over and over again. So from an economical aspect, it is seemingly superior.

In any case however, making either will likely lead you into some serious trouble with the law!!! :-)

[Edited on 11-6-2009 by -TheMadMen-]

Arrhenius - 11-6-2009 at 00:11

Sure, but you can't recover the Lewis acid catalyst

So if you use ferric chloride, you will use more lewis acid (on a molar basis) than yield product.

Law... eh.... I got a ticket for riding my bicycle on the sidewalk the other day. I could care less about the law.

-TheMadMen- - 11-6-2009 at 00:28

Ha ha, i like your attitude towards the law. Same same, straight from my heart. Heh. But i don't like jail that much......

So sometimes the law has to take first place.

And what you just said about the Lewis acid catalyst does indeed make sense, i forgot all about that, that's a bloody piss-off that is. Feeding the aluminum chloride into the reaction over and over again, never to see it again. It's a pity that aluminum chloride was not more available. I Am not that adept at my understanding of Lewis acid catalysts, but i would assume that aluminum chloride is both the cheapest and most economical of them all? From a practical standpoint. For friedel-crafts, at least for the home chemist?

I Don't want to veer off course, which i am, i am sure that there is a thread already for it, but i am going to say it right here, as far as preparing aluminum chloride goes, does the hydrochloric acid product, or the hydrolyzed form, work in friedel crafts? Or is it only the anhydrous form that works? Which is made by passing chlorine gas through molten aluminum? Hmm..... Food for thought hehe.....

Paddywhacker - 11-6-2009 at 00:48

Anhydrous only... same as FeCl3

But the Al does not need to be molten. You could pass dry Cl2 into Al powder in dichloromethane. Or use bromine or iodine instead of chlorine... that might be easier.

-TheMadMen- - 11-6-2009 at 00:54

Thanks for the advice Paddywhacker, i appreciate it. Is it possible to use any other solvent other than dichloromethane however? As funnily enough that is one thing i just don't have sitting around, either way, it beats having to make a furnace to contain molten Al anyday.

Arrhenius - 11-6-2009 at 08:56

It really makes more sense to buy it. FeCl3 is weaker than AlCl3, but will still work in most cases for friedel-crafts alkylation. FeCl3 is cheap, and I don't think you should worry about buying it. People are awfully paranoid here, but I think the headache gained by trying to make either of these lewis acids in an anhydrous fashion is worse. You cannot heat either of these to drive off water. Their hydrates are available everywhere, and are pretty useless unless you make metal art

Paddywhacker - 11-6-2009 at 12:58

If you are doing FC on a micro scale then it should be possible to prepare the catalyst in whatever solvent you are using for the FC from the metal powder and halogen, but really, as the previous poster said, anhydrous FeCl3 and anhydrous AlCl3 are not difficult to purchase.

Nicodem - 11-6-2009 at 14:22

You can not use AlCl3 for Friedel-Crafts allylation of benzene and certainly not with allyl chloride or bromide since allylbenzene reacts further with HCl/HBr to give a complex mixture of further alkylation products. It is done using ZnCl2 (or other suitable acids) and allyl alcohol. Check the literature.

-TheMadMen- - 18-6-2009 at 21:07

Where would one find Anhydrous AlCl3 to purchase? Chem supply store? Hardware store???

Arrhenius - 18-6-2009 at 21:51

Definitely not the hardware store, haha. A well stocked chemical supplier.

-TheMadMen- - 19-6-2009 at 00:28

Ohh, ahh i see:-) Hehe, i just remember some kind of chloride being sold at hardware stores, for welding or something, must have been ammonium chloride i guess......

I'll have to find a chemical supplier who can stock me up, ain't that easy to find many of ' em around here who will take on orders from the public.

pip - 25-6-2009 at 15:10

nicodem does the n-BuLi have to be in thf because in hexanes are more available not that I plan on doing it but an anagulous one with n-propylLi maybe.

Two things

Helgoland - 31-12-2009 at 18:21

1.Complete hydrogenation of cinnamaldehyde (from cinnamon oil) using a catalyst and elimination of remaining alcohol group
2. If one were interested - purely theoretical, of course, we're all law-abiding citizens, aren't we? - in amphetamines: Friedel-Crafts using acrylic acid chloride, addition of HCl (not BrCl) and Clemmensen reduction
I don't have any practical experience, so please tell me if this is total crap; but I hope this would work.

entropy51 - 31-12-2009 at 18:29

Total Crap
Why are you asking about amphetamines in a thread on allybenzene?

Did you get lost on the way to Wet Drums or the Heave?

bbartlog - 31-12-2009 at 19:56

He also asked about HCN in the methylamine thread. Seems to not have any idea that threads might actually be, you know, for the specified topic. And I thought I was a noob.

Helgoland - 8-1-2010 at 09:22

@entropy51: Because amphetamine might be synthesised from allylbenzene (I guess). If mentioning this was inappropriate, I apologise and would edit it if the edit button for that post hadn't disappeared.

@bbartlog: I thought it might be used in methylamine synthesis. If that's total crap, I apologise again. I know I'm a noob, so tell me when I get something wrong. But please read what I write first.

In order to (try to) contribute: What reduction method can be used for reducing both aldehydes and alkenes?

[Edited on 8-1-2010 by Helgoland]

CuReUS - 22-10-2016 at 01:13

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]

Maroboduus - 22-10-2016 at 15:01

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.

CuReUS - 22-10-2016 at 18:10

Quote: Originally posted by Maroboduus

Wouldn't using these various chloride Lewis acids to make allylbenzene give you a lot of phenyl 2-chloropropane?

they will.
nicodem has already explained this in the previous pagehttp://www.sciencemadness.org/talk/viewthread.php?tid=9310&a...

clearly_not_atara - 22-10-2016 at 19:58

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 595 times

[Edited on 23-10-2016 by clearly_not_atara]

Maroboduus - 23-10-2016 at 09:34

Quote: Originally posted by CuReUS

Quote: Originally posted by Maroboduus

Wouldn't using these various chloride Lewis acids to make allylbenzene give you a lot of phenyl 2-chloropropane?

they will.
nicodem has already explained this in the previous pagehttp://www.sciencemadness.org/talk/viewthread.php?tid=9310&a...

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.

Waffles SS - 24-10-2016 at 07:29

All possible way for synthesis of Allylbenzene by reaxys

Attachment: Allylbenzene.pdf (1.8MB)
This file has been downloaded 1658 times

Cryolite. - 24-10-2016 at 16:14

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.]

CuReUS - 25-10-2016 at 06:08

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?

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.

not anymore,A better method has been found https://en.wikipedia.org/wiki/Wolff%E2%80%93Kishner_reductio...

Cryolite. - 25-10-2016 at 09:30

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?

clearly_not_atara - 25-10-2016 at 17:57

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.

CuReUS - 25-10-2016 at 22:47

Quote: Originally posted by clearly_not_atara

I'm not sure that you can make p-toluenesulfonylhydrazine without going through hydrazine

http://onlinelibrary.wiley.com/doi/10.1002/jccs.200700220/fu...