Chemical Forums

Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: kk1 on November 04, 2011, 09:18:47 PM

Title: A question about blocking and removing at α-position
Post by: kk1 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?

(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fimg542.imageshack.us%2Fimg542%2F8558%2F85506977.jpg&hash=cc713242be5e5d2f5f586ac64e8db8410bdd7c29)

Thanks

Title: Re: A question about blocking and removing at α-position
Post by: Dan 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...