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Author Topic: Problem  (Read 2061 times)

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mpv

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Problem
« on: March 04, 2012, 10:44:59 PM »

Hope you'll enjoy this one ... Propose a mechanism for the following reaction.
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Dan

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Re: Problem
« Reply #1 on: March 04, 2012, 11:32:54 PM »

Is it thermally or photochemically induced?
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mpv

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Re: Problem
« Reply #2 on: March 04, 2012, 11:42:43 PM »

photochemically
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mpv

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Re: Problem
« Reply #3 on: March 06, 2012, 07:53:02 AM »

No takers... probably it's to easy for you guys.
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BobfromNC

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Re: Problem
« Reply #4 on: March 06, 2012, 08:52:16 AM »

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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mpv

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Re: Problem
« Reply #5 on: March 06, 2012, 09:09:13 AM »

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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BobfromNC

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Re: Problem
« Reply #6 on: March 06, 2012, 10:21:53 AM »

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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mpv

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Re: Problem
« Reply #7 on: March 06, 2012, 10:41:57 AM »

It's even more interesting, only one does a 2+2
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Arctic-Nation

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Re: Problem
« Reply #8 on: March 10, 2012, 06:23:11 AM »

If that's a first step, is the second an intramolecular Diels-Alder?
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mpv

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Re: Problem
« Reply #9 on: March 10, 2012, 09:20:39 AM »

Bingo. Can you propose a full mechanism.
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Arctic-Nation

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Re: Problem
« Reply #10 on: March 11, 2012, 08:21:35 AM »

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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