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Topic: Problem  (Read 6468 times)

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Offline mpv

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Problem
« on: March 05, 2012, 04:44:59 AM »
Hope you'll enjoy this one ... Propose a mechanism for the following reaction.
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Offline Dan

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Re: Problem
« Reply #1 on: March 05, 2012, 05:32:54 AM »
Is it thermally or photochemically induced?
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Offline mpv

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Re: Problem
« Reply #2 on: March 05, 2012, 05:42:43 AM »
photochemically
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Offline mpv

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Re: Problem
« Reply #3 on: March 06, 2012, 01:53:02 PM »
No takers... probably it's to easy for you guys.
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Offline BobfromNC

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Re: Problem
« Reply #4 on: March 06, 2012, 02:52:16 PM »
Here's my mechanism, a 2+2+2+2 to make a very sterically hindered intermediate, followed by a Cope rearrangement.   The intermediate may not exist for any detectable time.  Do I get a Scoobie snack?

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Offline mpv

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Re: Problem
« Reply #5 on: March 06, 2012, 03:09:13 PM »
Well you're not very far, but the dicyclopropane intermediate is very unlikely to form. Try thinking some classic photochemical reactions (Hint: only the cis form gives the final product).
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Offline BobfromNC

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Re: Problem
« Reply #6 on: March 06, 2012, 04:21:53 PM »
Do they propose that the 2 dienes each do a [2+2] reaction to form two cyclobutane rings and then those react/rearrange?  That also works for me, but still is a series of concerted reactions. 
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Offline mpv

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Re: Problem
« Reply #7 on: March 06, 2012, 04:41:57 PM »
It's even more interesting, only one does a 2+2
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Offline Arctic-Nation

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Re: Problem
« Reply #8 on: March 10, 2012, 12:23:11 PM »
If that's a first step, is the second an intramolecular Diels-Alder?
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Offline mpv

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Re: Problem
« Reply #9 on: March 10, 2012, 03:20:39 PM »
Bingo. Can you propose a full mechanism.
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Offline Arctic-Nation

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Re: Problem
« Reply #10 on: March 11, 2012, 02:21:35 PM »
Well, I've attached the mechanism I found, but I haven't checked whether Woodward-Hoffman agree with it or not. Everything looks awfully constrained, and I've never been good at electrocyclic reactions.
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