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Topic: Skattebol Rearrangement Question  (Read 4213 times)

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Offline zsinger

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Skattebol Rearrangement Question
« on: April 22, 2014, 07:35:39 PM »
All,
In the last step of the mechanism post Li-Halogen exchange, it indicates a ring expansion from 8 to 9 membered, with 2 alkenes oriented somewhat close to each other.  Is this ring expanding simply because of the instability of the carbanion produced, the torsional strain of the 3 membered ring which it relieves, or a combination of both?  Or something else :).  Any help appreciated.
                -Zack
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Offline AlphaScent

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Re: Skattebol Rearrangement Question
« Reply #1 on: April 23, 2014, 09:55:59 AM »
When you say close, do you mean allene close? right next to one another.  I havent looked at this in a while, but isnt it a carbene rearranging to an allene?
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Offline Archer

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Re: Skattebol Rearrangement Question
« Reply #2 on: April 23, 2014, 12:01:34 PM »
Can you attach the mechanism you are talking about? or at least provide the starting gem-dihalide?
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Offline AlphaScent

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Re: Skattebol Rearrangement Question
« Reply #3 on: April 23, 2014, 03:45:43 PM »
This is what I see for a general mechanism.  Zack, are you talking about cyclooctane-cyclopropane bicyclo system?
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Offline zsinger

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Re: Skattebol Rearrangement Question
« Reply #4 on: April 23, 2014, 04:09:38 PM »
Precisely!
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Offline AlphaScent

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Re: Skattebol Rearrangement Question
« Reply #5 on: April 23, 2014, 04:25:15 PM »
So I guess just apply the mechanism to the ring and you should have it.  I wonder how stable an nine membered cycloallene would be. 

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Offline Archer

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Re: Skattebol Rearrangement Question
« Reply #6 on: April 23, 2014, 04:52:37 PM »
These guys made it with a phenyl group attached using the above procedure.

http://onlinelibrary.wiley.com/doi/10.1002/jlac.199719970825/abstract

I am not sure of the significants of the phenyl group though as I don't have the full text. Possibly this inhibits spontaneous dimerisation.

C1CC=C=C(C2=CC=CC=C2)CCCC1
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