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Topic: An interesting Reaction  (Read 43280 times)

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Offline Heory

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Re: An interesting Reaction
« Reply #15 on: November 06, 2009, 07:50:40 AM »
No. Please deliberate on the problem before posting you answer. Don't just guess.

Offline Ulfsaar

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Re: An interesting Reaction
« Reply #16 on: November 06, 2009, 07:53:24 AM »
Well,but i have no patient……guss it is easier than to think it in my hard mind

Offline azmanam

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Re: An interesting Reaction
« Reply #17 on: November 06, 2009, 09:58:56 AM »
So I see what looks like a donor/acceptor epoxide that looks like a latent dipole and an alkene waiting to be a dipolarophile.  I suspect you'll get a 3+2 dipolar cycloaddition.  Followed by lactam formation to give a stable trans 6/5 fused ring system?  I chose the regioselectivity of the double bond because the more substituted side is "more carbocation like" and I predicted that side to interact with the "more carbanion/enolate like" side of the epoxide.  I chose the facial selectivity of the double bond to put the methyl group away from the aryl group on the one side and the alkylamine group away from the ester on the other.
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Offline Heory

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Re: An interesting Reaction
« Reply #18 on: November 06, 2009, 10:21:23 AM »
Very novel idea, azmanam! Is this kind of 1,3-dipolar cycloaddition involving an epoxide supported by any document?
I quite agree with the resonance structure(very good idea! ), though actually the reaction didn't take place in that way. My frist hint will be that we shall consider why the ester group was designed next to the epoxy group.The ester group is not just an EWG.
« Last Edit: November 06, 2009, 10:38:30 AM by Heory »

Offline azmanam

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Re: An interesting Reaction
« Reply #19 on: November 06, 2009, 10:38:14 AM »
sure, you can use epoxides.
http://dx.doi.org/10.1002/anie.197705721

You can also add a carbene to an aldehyde to get the same 1,3-dipole
http://dx.doi.org/10.1021/ja00382a039

But that's really not the pathway?  huh.  I was convinced
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Offline Heory

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Re: An interesting Reaction
« Reply #20 on: November 06, 2009, 10:43:41 AM »
what a pity i have no access to the data base. The reaction didn't react in that way, mabe because of the different reaction conditions.
Dood night! See your new idea tomorrow.

Offline azmanam

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Re: An interesting Reaction
« Reply #21 on: November 06, 2009, 01:03:05 PM »
ok, try number two is initial formation of the amide followed by acid promoted epoxide opening to give a 7-membered ring.
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Offline azmanam

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Re: An interesting Reaction
« Reply #22 on: November 06, 2009, 01:47:02 PM »
Until Heory wakes back up, perhaps we can discuss this one amongst ourselves?  I don't really like my second guess, because it just doesn't 'look right.'  ya know?  I don't see any driving reason why someone would want to make a 7-membered lactamether with a benzyllic bromide.  I suspect amide formation will happen first under strongly acidic conditions, but from there, I don't know what direction to turn.  Is that the end of the aqueous acid step?  Does the epoxide and alkene really survive the acidic conditions?  What else might we do after amide formation?
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Offline nj_bartel

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Re: An interesting Reaction
« Reply #23 on: November 06, 2009, 01:59:14 PM »
Well, I'm thinking your second proposal is wrong based on his hint alone.  Still looking a little deeper to see if I can point you somewhere else.  Idk, this doesn't seem too reasonable, but what about intramolecular lactone formation (4-membered ring) followed by amide formation to get the B-lactam?  It would at least be something someone might aim to make.
« Last Edit: November 06, 2009, 02:11:54 PM by nj_bartel »

Offline azmanam

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Re: An interesting Reaction
« Reply #24 on: November 06, 2009, 02:18:50 PM »
I was just drawing out a b-lactam forming process, too!  mine goes through a bit different pathway than what you're describing, I think.  That's only step 1, though.  I don't know what to do w/ step 2.  Just addition of HX to an alkene?
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Offline nj_bartel

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Re: An interesting Reaction
« Reply #25 on: November 06, 2009, 02:23:25 PM »
You did go through a different mechanism, but yeah, same end product.  I wasn't really sure where to take it from there.  Just brominating the alkene definitely seems too simple, but carbocation formation doesn't really leave attack open to anything except that bromide.

Offline Ulfsaar

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Re: An interesting Reaction
« Reply #26 on: November 06, 2009, 09:08:07 PM »
Some thing may be wrong i'm confusing about this question

Offline Heory

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Re: An interesting Reaction
« Reply #27 on: November 06, 2009, 10:06:31 PM »
nj_bartel, good idea. Beta-lactam is indeed the necessary part of antibiotics thus bound to be aimed to make by someone. But the structure you desire for wasn't formed.
azmanam, there's another path for step 1. BTW, I like your arrow pushing in the formation of the beta-lactam. Every time I draw a nucleophlic replacement of a ester by a nucleophlic reagent, I have to divide it into 2 steps. You used the most concise pattern.
Ulfsaar, good idea. But the first step is not pinacol rearrangement and I don't understand the following rearrangement. Would you please be more descriptive?

Since we were all off the track, I'll give the second hint:

Remember the reaction was performed in aqueous solution. Bonus: name the reaction in the first step.

Offline Heory

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Re: An interesting Reaction
« Reply #28 on: November 07, 2009, 10:00:58 PM »
HINT 3:
Which named reaction can be used to achieve the transformation RCHO--->RCH2CHO?

Offline Ulfsaar

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Re: An interesting Reaction
« Reply #29 on: November 08, 2009, 02:53:57 AM »
Dazon reaction? a good idea!!

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