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Author: Subject: Phenethyl tosylate from styrene oxide?
Klute
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[*] posted on 15-7-2009 at 02:40
Phenethyl tosylate from styrene oxide?


I'm looking for a way of forming phenethyl tosylate from styrene oxide...

Now, styrene oxide can be easily reduced to 2-phenylethanol with a variety of reagents: hydrogenation over catalysts link, NaBH4 link, LiAlH' diborane, etc link

Now, in order to avoid doing two reactions (reduction + tosylation or halogenation), I would like to know if anyone has a idea for a one pot solution... Addition of tosyl acid directly to the epoxide doesn't look feasible, and would yield the b-hydroxytsulfonate acid if I am not wrong, provided it even works...

ANy ideas?

[Edited on 15-7-2009 by Klute]




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unome
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[*] posted on 19-10-2009 at 12:45


Here is a paper on the isomeric ring opening reactions of Styrene Oxide with acid (in this case AcOH)

Attachment: Rxns.of.monomeric.styrenes.pdf (1.5MB)
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Attachment: Isomeric.RingOpening.Styrene.Oxide.pdf (350kB)
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Theophrastus_2
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[*] posted on 25-10-2009 at 06:46


I'm sorry if I'm throwing the thread off topic (as the answer to the question, has already been alluded to in unome's links), but how did you manage to make styrene oxide? Direct oxidation of styrene in this case would be no good, as it would form the diol. The only method I know of involves use of peracids. (I know in the first paper, perbenzoic acid was cited for this purpose) So I'm wondering... how'd you do it?
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[*] posted on 25-10-2009 at 16:43


You can epoxidize styrene with buffered peracids or mCPBA in DCM. Or you can make it catalytically (and enantiopure) with something like Jacobsen's catalyst + bleach.

I don't see a feasible 1 step reaction. Why? In order to get to your desired product, you would need the epoxide to act as a nucleophile to attach the tosyl moiety. Styrene can rearrange to phenylacetaldehyde, but that's in the wrong oxidation state, and still not nucleophilic. Styrene oxide is one oxidation state above phenethyl alcohol (it's oxidation state is equivalent to the diol), so it must undergo reduction.

Also, tosic acid is a monohydrate, and as such will probably open the epoxide like a shot. Tosylate is also not a good nucleophile, so you wouldn't even get the alpha-hydroxy tosylate.

styrene_oxide_oxid_st.gif - 5kB

[Edited on 26-10-2009 by Arrhenius]
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[*] posted on 26-10-2009 at 11:30


Quote: Originally posted by Theophrastus_2  
I'm sorry if I'm throwing the thread off topic (as the answer to the question, has already been alluded to in unome's links), but how did you manage to make styrene oxide? Direct oxidation of styrene in this case would be no good, as it would form the diol. The only method I know of involves use of peracids. (I know in the first paper, perbenzoic acid was cited for this purpose) So I'm wondering... how'd you do it?

You really should improve your literature searching skills. There are hundreds of papers about styrene epoxidations and dozens of reagents described. Among the most easily available to an average amateur are bleach (sodium or calcium hypochlorite), H2O2, trichloroisocyanuric acid (TCCA), sodium percarbonate, sodium perborate and Oxone. Here is one example employing TCCA:

Quote:
Synthesis of styrene oxide:

Into a 500ml flask with a thermometer was added 30g of styrene, 240ml acetone and 60ml water. The flask was immersed in a cold water bath and magnetic stirring was applied. A solution of 24.4g TCCA in 100ml acetone was added through an addition funnel at such a rate that the temperature never went above 30°C. This took about half an hour and a precipitate of cyanuric acid start to form after the first third of TCCA was added. The mixture was left stirring 45 more minutes and the unreacted TCCA quenched with the addition of 0.5g Na2SO3. Five minutes later, 50ml of 10M aqueous NaOH, was slowly added drop-wise. The temperature rose from 25 to 32°C and two phases formed. The lower, minor one was a white slurry while the upper acetone solution was clear. After stirring for an additional 1:30h the upper phase was separated by decantation. It was then washed with 50ml brine. The acetone was distilled off and the remaining mixture distilled under the vacuum of an aspirator. At about 50°C water with a few drops of the product that steam distilled came over, followed by the product at 100-140°C. Some yellow gelatinous side product remained in the flask. The distillate was dried over Na2SO4. It was slightly denser than water, clear, with a slightly sweet smell without any residual styrene smell and amounted to 25.15g (73%). The IR spectrum is identical to the published for styrene oxide.




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