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Topic: Retrosynthesis question  (Read 2895 times)

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Offline spidermclovin

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Retrosynthesis question
« on: November 28, 2018, 09:26:05 AM »
A retrosynthetic question asks for the synthons, real reagents and synthesis from the disconnection attached (shown in red). The alcohol group in this molecule makes grignard reagents unusable. Any ideas?
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Offline sjb

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Re: Retrosynthesis question
« Reply #1 on: November 28, 2018, 10:15:46 AM »
What reactions do Grignards undergo?
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Offline Babcock_Hall

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Re: Retrosynthesis question
« Reply #2 on: November 28, 2018, 02:24:44 PM »
What other reactions do you know that form C-C bonds?
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Offline rolnor

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Re: Retrosynthesis question
« Reply #3 on: November 29, 2018, 10:07:08 AM »
This could work, thiophene-chemistry:
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Offline rolnor

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Re: Retrosynthesis question
« Reply #4 on: November 29, 2018, 10:09:26 AM »
Sorry for messy scheme, the cyclohexyl thiophene is lithiated with n-BuLi.
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Offline kriggy

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Re: Retrosynthesis question
« Reply #5 on: November 29, 2018, 03:42:30 PM »
what about conjugated 1,6 addition and then reduction of the ketone and double bonds?
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Offline clarkstill

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Re: Retrosynthesis question
« Reply #6 on: November 30, 2018, 04:03:32 AM »
Quote from: rolnor on November 29, 2018, 10:07:08 AM
This could work, thiophene-chemistry:

I've literally never seen that before but it's neat - thiophene as a masked n-butyl group!

I was thinking along the lines of a Wittig-hydrogenation (attached)...
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Offline rolnor

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Re: Retrosynthesis question
« Reply #7 on: November 30, 2018, 05:41:11 AM »
The Wittig-reagent is very basic and it could be quenched by the OH-group? Perhaps a protection-group?
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Offline wildfyr

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Re: Retrosynthesis question
« Reply #8 on: November 30, 2018, 09:46:18 AM »
That thiophene trick is really great!
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Offline rolnor

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Re: Retrosynthesis question
« Reply #9 on: November 30, 2018, 10:59:07 AM »
Thanx wildfyr! :)
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Offline clarkstill

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Re: Retrosynthesis question
« Reply #10 on: November 30, 2018, 11:37:21 AM »
Quote from: rolnor on November 30, 2018, 05:41:11 AM
The Wittig-reagent is very basic and it could be quenched by the OH-group? Perhaps a protection-group?

I don't think it's a problem, people tend to just use 2 eq. of the ylide, e.g. compound 9 here:

https://pubs.acs.org/doi/suppl/10.1021/jo8017704


... but I concede the thiophene method looks much more fun.
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