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Topic: Problem of the Week - 08/31/09  (Read 17509 times)

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Offline azmanam

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Problem of the Week - 08/31/09
« on: August 31, 2009, 09:52:48 AM »
So, after a brief hiatus, we're back with a vengeance.  Put on your conformational analysis hat, and dive right into this week's problem.

QUESTION: Provide a complete, arrow-pushing mechanism for the following transformation.  Bonus: name any named reactions involved.
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Offline Ida Isotope

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Re: Problem of the Week - 08/31/09
« Reply #1 on: August 31, 2009, 10:02:51 AM »
Reaction Mechanisms is my weakness! I'm glad you post this. Out of curiousity...is this considered an advanced organic chem question?

Offline azmanam

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Re: Problem of the Week - 08/31/09
« Reply #2 on: August 31, 2009, 10:45:41 AM »
Yes, this is considered an advanced question... but don't be daunted.  The mechanism is quite doable.
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Offline blind

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Re: Problem of the Week - 08/31/09
« Reply #3 on: August 31, 2009, 12:04:53 PM »
Perhaps something like this?


Offline azmanam

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Re: Problem of the Week - 08/31/09
« Reply #4 on: August 31, 2009, 12:08:40 PM »
almost.  no acid in solution.
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Offline blind

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Re: Problem of the Week - 08/31/09
« Reply #5 on: August 31, 2009, 12:14:04 PM »
Hm...does it go through some zwitterion TS?

Offline azmanam

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Re: Problem of the Week - 08/31/09
« Reply #6 on: August 31, 2009, 12:20:36 PM »
nope :)  and be more specific with one of your named reactions
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Offline blind

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Re: Problem of the Week - 08/31/09
« Reply #7 on: August 31, 2009, 12:26:49 PM »
First step - Oxy-Cope, Second step - Claisen?

Not sure how to go from my second intermediate to the final product...

Offline azmanam

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Re: Problem of the Week - 08/31/09
« Reply #8 on: August 31, 2009, 12:27:53 PM »
sounds good so far.  make sure you can account for all the stereochem at the end
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Offline blind

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Re: Problem of the Week - 08/31/09
« Reply #9 on: August 31, 2009, 12:30:32 PM »
Yeah, aside from the R2/R3 groups, stereochem fit product..

The drawing above was missing some stuff, here's the revised one, although it sounds like it wouldn't make much of a difference...

Offline Ida Isotope

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Re: Problem of the Week - 08/31/09
« Reply #10 on: August 31, 2009, 11:16:24 PM »
I've never heard of either of those synthesis reactions. I am taking advanced organic chem this fall though so I guess I should get familiar with them.

Offline nj_bartel

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Re: Problem of the Week - 08/31/09
« Reply #11 on: September 01, 2009, 12:46:02 AM »
I can never predict these darned rearrangements with any success :/

Offline azmanam

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Re: Problem of the Week - 08/31/09
« Reply #12 on: September 01, 2009, 06:02:09 AM »
Quote
I am taking advanced organic chem this fall though so I guess I should get familiar with them.

There are all sorts of interesting pericyclic reactions you'll learn as apart of your course.  the ones in this mechanism are some of the common ones, so I'm sure you'll be introduced to them - prolly in this adv organic class you're taking.

Quote
I can never predict these darned rearrangements

pericyclic reactions are my favorite mechanism type.  Is that weird that I have a favorite mechanism?  imho the hardest part is seeing it in 3d and predicting the stereochem.  the stereochem of the oxy cope is still not predicted by the drawn conformation, wanna give that a try?

Quote
here's the revised one

still no acid in sol'n.  the third step's not quite right yet.
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Offline nj_bartel

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Re: Problem of the Week - 08/31/09
« Reply #13 on: September 01, 2009, 09:35:11 AM »
No it's not weird :P.  I think the problem is we skipped pericyclics at my school.  Gonna have to give that chapter a read when I get some free time.

Offline Dan

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Re: Problem of the Week - 08/31/09
« Reply #14 on: September 01, 2009, 11:16:07 AM »
I reckon it ends with an Ene reaction, see scheme

Edit: Ahh, but my stereochem turned out wrong...
« Last Edit: September 01, 2009, 11:30:05 AM by Dan »
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