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Topic: Synthesis  (Read 4958 times)

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Offline John Mcmurry

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Re: Synthesis
« Reply #15 on: August 14, 2018, 02:00:22 PM »
How do I create the cyclopentane without that "extra" bond? I have to use a butane with some kind of terminal groups, right?

Offline Babcock_Hall

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Re: Synthesis
« Reply #16 on: August 14, 2018, 02:48:35 PM »
I would consider reversing the polarities of the two pieces that you are trying to bring together.

Offline wildfyr

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Re: Synthesis
« Reply #17 on: August 14, 2018, 03:24:50 PM »
Oops, I didnt look closely enough. The cuprate route isn't the way to go.

I agree with using butane with 2 terminal groups. Babcock is on the track I was originally thinking. What is another type of chemistry that a methylene alpha to a carbonyl can do? And two carbonyls even better.

Offline rolnor

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Re: Synthesis
« Reply #18 on: August 15, 2018, 06:01:45 AM »
I think if you mix this enone with base you will get dimer or polymer, Michael-addition. Also if you try to remove the carbonyls with Woolf-Kischner you will have attack by hydrazine on the double-bond.

Offline wildfyr

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Re: Synthesis
« Reply #19 on: August 15, 2018, 09:17:37 AM »
That makes this quite a difficult substrate rolnor.

Offline Babcock_Hall

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Re: Synthesis
« Reply #20 on: August 15, 2018, 10:22:54 AM »
Perhaps self condensation (polymerization) could be minimized by the appropriate choice of addition of reagents, but I don't have direct knowledge.  I also wonder whether or not a plausible route, especially if possible side reactions are acknowledged, might be good enough for the purposes of this problem.

Offline sjb

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Re: Synthesis
« Reply #21 on: August 15, 2018, 10:55:48 AM »
How about protection of the double bond - e.g. with Br2 which you may be able to reduce back off with zinc, or as the epoxide (and then removal with PPh3?)

Just some random thoughts

Offline wildfyr

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Re: Synthesis
« Reply #22 on: August 15, 2018, 11:08:57 AM »
I'm kicking myself sjb, because I had the exact same two thoughts (bromination or epoxidation), then discarded them because I couldnt think of how to to "deprotect" the double bond correctly.

Offline sjb

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Re: Synthesis
« Reply #23 on: August 15, 2018, 05:11:20 PM »
Hah, I was just looking through some old notes earlier and thought of the thread :) Not sure about the epoxidation route now I think it through, it is more used to invert the ene geometry so I don't think will be effective here.

Offline wildfyr

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Re: Synthesis
« Reply #24 on: August 15, 2018, 06:14:04 PM »
If you react an epoxide with LAH you'll get an alcohol, which can be dehydrated with a strong acid. That's a nice route.

https://pubs.acs.org/doi/pdf/10.1021/ja01038a042

Offline rolnor

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Re: Synthesis
« Reply #25 on: August 16, 2018, 04:22:09 AM »
I think the epoxide can be converted back to alkene with PPh3 but epoxides are also electrophiles and can react if base is added.

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