Opylation
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Alpha-alkylStyrene from polystyrene
I’ve been thinking about the difficulty of making a-alkylstyrene, besides a-methylstyrene, without using difficult to obtain/create, or expensive,
catalysts. I believe I have thought of a relatively straightforward way to prepare a-alkylstyrenes from styrene polymers however I am curious if this
is relatively feasible. Please let me know what you think or if you think there might be a better way.
This synthesis can be accomplished from styrene monomers. This itself can be produced from styrofoam (polystyrene). Now, this is a long synthesis,
but, it is cheap.
Styrene is oxidized to styrene oxide via peracid
Styrene oxide can be isomerized to phenylacetaldehyde
Phenylacetaldehyde can be alkylated with alkyl halide
a-alkylphenylacetaldehyde can then be used in reductive amination to form b-alkylphenethylamine
This can now be either:
* Perform a double alkylation of the amine to form a tertiary amine and then perform a Cope elimination
Or
* Perform a triple alkylation of the amine to form a quaternary amine and then perform a Hofmann elimination
forming a-alkylstyrene
Now, I have only done an hour or two of research so this may not be that feasible. I mean phenylacetaldehyde seems to be extremely reactive but maybe
limiting the temperature during isomerization from styrene oxide as well as during its alkylation. I really just want to start a conversation about
it.
I know there may be quicker and easier routes to a-alkylstyrenes like for instance terminal olefinations from ketones using certain reagents however
some are pyrophoric and some are expensive, and some are both. Anyways, I digress
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clearly_not_atara
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Selective monoalkylation of phenylacetaldehyde would probably require a Stork reaction. The subsequent reduction is better performed with
tosylhydrazine. If you insist on attempting a Hofmann elimination, the more prudent approach would be reduce to the alcohol, brominate, and react with
trimethylamine. I know very little about the Cope rxn.
But the more reasonable approach would be to use benzoic acid as the precursor, and destructive distillation with the Ca alkanoate of your choice (up
to about caprylic) to obtain the alkanophenone. Then a Wittig olefination gives the styrene directly. Triphenylphosphine is not expensive or
dangerous. But some people just don't want to deal with the chemical companies.
If the Wittig is unavailable, a Reformatsky reaction with ethyl chloroacetate or similar gives the corresponding alpha-alkylhydrocinnamate ester,
which can be dehydrated using acid to the cinnamate with the desired regioselectivity. Hydrolysis and decarboxylation gives the styrene. Fusing the
Reformatsky product with NaOH might do it all in one go.
[Edited on 11-3-2020 by clearly_not_atara]
[Edited on 04-20-1969 by clearly_not_atara]
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Tamerlane
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Polystyrene is most likely a fool's errand. I think a feasible way to prepare, for example, alpha methylstyrene would be to condense acetophenone with
a malonate or cyanoacetate according to known methods. This would yield a phenylethylidene malonic acid after hydrolysis, which decarboxylates easily to beta-methylcinnamic
acid. Decarboxylating the substituted cinnamic acid would give the substituted styrene. I don't know how easily this would occur, but it's probably
easier than decarboxylating regular cinnamic acid.
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Opylation
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Tamerlane: a-methylstyrene is easiest made by dehydration of cumyl alcohol which can be easily made via grignard.
Atara: I’m not so sure a stork reaction would be required to alkylate the alpha carbon on phenylacetaldehyde. There is only one alpha carbon to the
carbonyl and it sits between two electron withdrawing groups: the carbonyl and the benzene ring. In fact, the pka of the alpha hydrogen is only 15. Im
sure an alkoxide, like tert-butoxide, or some stronger base like sodium amide or some alkaline metal hydride could deprotonate are the alpha carbon
I am going to have to take a look at the other reactions you’ve mentioned though. I love working through the steps
[Edited on 11-3-2020 by Opylation]
[Edited on 11-3-2020 by Opylation]
[Edited on 11-3-2020 by Opylation]
[Edited on 11-3-2020 by Opylation]
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draculic acid69
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I'd say polystyrene is a decent source for styrene but if starting with the foam like I once tried you'll need a 20l paint can to melt the foam into a
solid disc which can then be crushed and used like polystyrene knives and forks to destructively distill into styrene point being start with the
knives and forks not the foam.also styrene is cheap when bought off eBay.better off starting with that.
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Opylation
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I heard it’s easiest to use acetone to dissolve the polymer and make it easy to work with since it’s soluble. I think I saw one video where this
guy was able to condense like 10-15L of styrofoam into a tiny puck with acetone
[Edited on 11-3-2020 by Opylation]
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Opylation
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Tamerlane: I was looking at that synorg page you posted and starting from an alkylphenone that would be a perfect way to proceed to a Hofmann or Cope
elimination. After the condensation of the alkylphenone and cyanoacetate ester, a decarboxylation and then reduction to amine and all that’s left to
do is alkylate and then perform the elimination. I like it 
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