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Topic: Retrosynthesis Help  (Read 2725 times)

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Offline n0vice

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Retrosynthesis Help
« on: May 21, 2012, 12:40:33 PM »
I just finished working on this synthesis problem my teacher gave me, but I'm feeling kind of uncomfortable with the path that I drew up. If someone could check this I would really appreciate it.
http://imgur.com/a/BpDHF

NBS, Corey-House, alkyne, oxidative cleavage, and free radical halogenation reactions are banned.

Thanks

Offline Dan

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Re: Retrosynthesis Help
« Reply #1 on: May 22, 2012, 03:14:34 AM »
I haven't been through thoroughly, but steps 4 and 5, where you a conjugate addition to an unsaturated ketone, will probably react further (Robinson ring annulation). You can then simply alkylate the Robinson product in one step with base/MeBr. That saves you 8 steps.
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Offline orgopete

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Re: Retrosynthesis Help
« Reply #2 on: May 22, 2012, 03:49:27 PM »
These are difficult questions to discuss. (It is also advantageous to attach the scheme directly in the post so we don't have to follow a link and potentially leads to a broken link if the server stops hosting the original scheme, use Additional Options…)

It is useful to see where the start and end are, but I find it difficult to comment upon a scheme. If a false step is proposed in step one, what effect does that have on the remainder to the scheme?

Was an electrophilic addition to benzene taught in class with a haloketone or as a ketal of a haloketone? I would have some anxiety about it undergoing a rearrangement by non-bonded electrons participating with the carbocation intermediate.
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Offline n0vice

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Re: Retrosynthesis Help
« Reply #3 on: May 22, 2012, 08:51:45 PM »
Thanks you guys so much for your advice. Dan thanks for pointing that step out to me. That was the step I was feeling the most uneasy about and you really cleared it up.


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