Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Altered State on October 23, 2013, 08:45:39 PM
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In this problem I need to propose a good method to do these transformations:
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FAaCQWQ3.png&hash=14dce5e70996f105377a4ecca018cfbfdfe750f2)
I know there are some different ways, but I have to do it using sulphur chemistry.
For the first one, I thought of a alpha-halogenation, and then, Swern reaction (DMSO, heat) to give 1,2-diketone
Then use Julia olephination to give the alkene. I guess I'll need to protect one of the carbonyl (after alpha-halogenation and before Swern oxidation).
But I see this method kind of "overcomplicated", any other idea?
For the last one I'm gonna need some hints, because I see the possibility of epoxide opening and then elimination. But that does not involve sulphur compounds chemistry, which I need to use.
Thanks in advance
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My idea for 1 would be Julia olefination, riley oxidation, swern oxidation.
For two the best thing i came up with is Ring opening with hydroxy, mono tosylation followed by elimination.
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For the first one, check out the reaction of trimethylsulfoxonium iodide with cyclic ketones in the presence of a strong base (KOtBu, I think). It's related to the Corey-Chaykovsky reaction, but rather than giving the epoxide, you can get the a,b-unsaturated ketone you describe. It's one step from the ketone, and I know that that EXACT reaction is in the literature because we had an undergrad student running it last year!
If you have access to SciFinder, search for that reaction; otherwise Google should find it for you.
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For the first one, check out the reaction of trimethylsulfoxonium iodide with cyclic ketones in the presence of a strong base (KOtBu, I think). It's related to the Corey-Chaykovsky reaction, but rather than giving the epoxide, you can get the a,b-unsaturated ketone you describe. It's one step from the ketone, and I know that that EXACT reaction is in the literature because we had an undergrad student running it last year!
If you have access to SciFinder, search for that reaction; otherwise Google should find it for you.
I serached that reaction and I see how this reaction works, but I don't see how can it yield a,b-keto-alkene and not the epoxide...
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If you want to use sulfur, why not use the sulfoxide elimination reaction in as used in the "annelation and elimination" question you posted?
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If you want to use sulfur, why not use the sulfoxide elimination reaction in as used in the "annelation and elimination" question you posted?
How would you add CH2S(O)Ph group?
Just make enloate of ketone and then add Br-CH2-S(O)-Ph?
Or better add Br-CH2-S-Ph and then oxidize with NaIO4/MeOH
And then heating would give the product of beta elimination
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I'd choose the "Or better…" route. You should be able to do the allylic alcohol the same strategy, sulfide, sulfoxide, and elimination.