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Topic: A question about blocking and removing at α-position  (Read 2480 times)

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Offline kk1

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A question about blocking and removing at α-position
« on: November 04, 2011, 09:18:47 PM »
Hello,

I want really to know this way.

I am reading a book on organic chemistry. and it explains..

to block an α-position, it uses ii, BuSH, TsOH. and
to remove the one, it uses KOH H2O ethylene glycol, reflux.

I can understand the blocking. but I could not understand the removing with KOH H2O ethylene glycol, reflux.

Could not you teach me the mechanism just on the removing, this?



Thanks

Offline Dan

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Re: A question about blocking and removing at α-position
« Reply #1 on: November 05, 2011, 08:03:45 AM »
Ethylene glycol is just a very high boiling solvent.

The deprotection is hydrolysis of the enol thioether, followed by a reverse Claisen.

Start with a Michael addition of hydroxide and see what you get...
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