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Topic: Diels Alder  (Read 3302 times)

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Offline AlphaScent

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Diels Alder
« on: April 19, 2015, 05:22:13 PM »
Do you think I can get this reaction to go to completion?  Maybe heat and Lewis acid??  Is the diene reactive enough?

(I know cyclopentadiene is very reactive and will be more so with a activating methyl group)

The homoketone (unconjugated) bothers me a bit but it is the only way to get the synthesis I want.  I can show the rest if someone would like.
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Offline discodermolide

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Re: Diels Alder
« Reply #1 on: April 19, 2015, 08:42:37 PM »
You probably don't need the catalyst. That will tie up the 2 carbonyls.
But you need to think about the stereochemistry of the product. That chiral auxiliary will have some effect.
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Offline AlphaScent

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Re: Diels Alder
« Reply #2 on: April 19, 2015, 08:52:09 PM »
Hmm... I was going off of notes from class and worked out the TS and believe I have the right stereochemistry.

I have been known to be wrong though haha.

Attached is what is in the notes given by the professor.

Cheers!
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Offline AlphaScent

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Re: Diels Alder
« Reply #3 on: April 19, 2015, 08:55:52 PM »
Wait....The diene will approach from the opposite face of the auxillary....The notes and I are wrong!!!

The auxillary should be the other way, correct??

The fact the double bond is trans also makes me think.  Is that the Endo product...seems to me it is.
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Offline discodermolide

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Re: Diels Alder
« Reply #4 on: April 19, 2015, 09:22:13 PM »
which C=C are you talking about, the one in the first scheme or the second one?
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Offline AlphaScent

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Re: Diels Alder
« Reply #5 on: April 19, 2015, 09:52:09 PM »
The C=C from the second scheme is straight from my notes given by the professor. 

The first is my method for a reaction in a synthesis. 

I have to think if the C=C with the methyl (methylcyclobutadiene) will be on the correct side (regiochemistry).

I am referring to the first scheme.  I may have my regiochemistry wrong.
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Offline discodermolide

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Re: Diels Alder
« Reply #6 on: April 19, 2015, 10:04:37 PM »
OK, well is the top face of the C=C not blocked by the auxiliary?
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Offline orgopete

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Re: Diels Alder
« Reply #7 on: April 20, 2015, 10:28:26 AM »
I have little faith in my ability to predict a reaction's enantioselectivity, so I cannot make those predictions. I'd simply use the example from your notes as a guide. However, you've made a significant change in the dienophile by moving the double bond. I'd doubt you'd get that product.
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Offline AlphaScent

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Re: Diels Alder
« Reply #8 on: April 20, 2015, 12:40:47 PM »
Orgopete,

I agree. The dieneophile is no longer electron poor.  Some thought must be taken. 

I will post my answer to the question.  It may be completely wrong.
If you're not part of the solution, then you're part of the precipitate

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