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Topic: Cyclization  (Read 2218 times)

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Offline Messi

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Cyclization
« on: January 20, 2013, 01:04:31 PM »
Hi guys,

I showed a transformation below. I was wondering what the mechanism was. Simply telling me in words would be great. Just a little confused :)

Thanks!

Offline sjb

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Re: Cyclization
« Reply #1 on: January 20, 2013, 04:30:21 PM »
Do you have any thoughts? Is there anything missing in the arrows that you've cropped in the formation of 100?

Offline Messi

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Re: Cyclization
« Reply #2 on: January 20, 2013, 05:20:52 PM »
I really have no clue where to start. I do have an idea that the lone pairs of the Nitrogen is attacking the either a hydrogen or the triple bond. Can I have a hint perhaps? :)

No, the arrow comes from another molecule being synthesized into that molecule. I took this picture from a paper.

Offline discodermolide

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Re: Cyclization
« Reply #3 on: January 20, 2013, 06:51:27 PM »
Are there any reagents given for the reaction of 100 to 101?
What is obvious is the acetylenic ether here.
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Offline Messi

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Re: Cyclization
« Reply #4 on: January 20, 2013, 11:30:47 PM »
No, no reagents. All I know is that addition of100 to refluxing xylene a followed by heating at this temp for 3hours generated the desired δ-lactam 101. I was just unsure about the mechanism.

Offline orgopete

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Re: Cyclization
« Reply #5 on: January 22, 2013, 09:52:49 AM »
Formally, this reaction is unbalanced, therefore some information is missing. The terminal acetylenic carbon has the oxidation state of a carboxylic acid or ester. Cyclization should be more easily accomplished at that stage. If the reaction were to follow that path then a mineral acid and/or mercury salts could catalyze it.

It could be possible for the amine to add to the acetylene, and then a Cope-like electrocyclic elimination of ethylene. I would not expect this mechanism unless this mechanism has been discussed in class (which I skipped).
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