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Topic: Best way to do these transformations using Sulfur chemistry  (Read 2027 times)

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Offline Altered State

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Best way to do these transformations using Sulfur chemistry
« on: October 23, 2013, 08:45:39 PM »
In this problem I need to propose a good method to do these transformations:



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

Offline mst

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Re: Best way to do these transformations using Sulfur chemistry
« Reply #1 on: October 24, 2013, 05:28:43 AM »
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.

Offline ziqquratu

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Re: Best way to do these transformations using Sulfur chemistry
« Reply #2 on: October 24, 2013, 07:50:28 AM »
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.

Offline Altered State

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Re: Best way to do these transformations using Sulfur chemistry
« Reply #3 on: October 24, 2013, 10:14:03 AM »
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...

Offline orgopete

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Re: Best way to do these transformations using Sulfur chemistry
« Reply #4 on: October 24, 2013, 10:33:43 AM »
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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Offline Altered State

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Re: Best way to do these transformations using Sulfur chemistry
« Reply #5 on: October 24, 2013, 10:48:25 AM »
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

Offline orgopete

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Re: Best way to do these transformations using Sulfur chemistry
« Reply #6 on: October 24, 2013, 04:12:12 PM »
I'd choose the "Or better…" route. You should be able to do the allylic alcohol the same strategy, sulfide, sulfoxide, and elimination.
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