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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: wintermute on January 17, 2007, 10:13:43 AM

Title: decarbonylation of alpha-acetyl-beta-ketoester - mechanism needed
Post by: wintermute on January 17, 2007, 10:13:43 AM

hi all,

i am puzzled with this transformation. can anybody provide me with the hint, please?

thanks in advance

Title: Re: decarbonylation of alpha-acetyl-beta-ketoester - mechanism needed
Post by: FeLiXe on January 17, 2007, 11:23:51 AM

the start will probably be a deprotonation of the H that is alpha to three carbonyls because it is the most acidic one

Then you'll need a hydrogen shift and ethanol leaves (I guess)

Title: Re: decarbonylation of alpha-acetyl-beta-ketoester - mechanism needed
Post by: movies on January 17, 2007, 12:40:49 PM

Actually deprotonating the H between the three carbonyls won't get you anywhere (although you're right that it is the most acidic proton).  Think about using OH- as a nucleophile, or think about what else you have in solution that you could deprotonate.

Title: Re: decarbonylation of alpha-acetyl-beta-ketoester - mechanism needed
Post by: FeLiXe on January 17, 2007, 06:26:50 PM

having fun using the "socratic way" ?  :)

how about this: reverse Claisen-condensation  8)

Title: Re: decarbonylation of alpha-acetyl-beta-ketoester - mechanism needed
Post by: movies on January 17, 2007, 07:53:33 PM

Quote from: FeLiXe on January 17, 2007, 06:26:50 PM

how about this: reverse Claisen-condensation  8)

There you go.

Title: Re: decarbonylation of alpha-acetyl-beta-ketoester - mechanism needed
Post by: wintermute on January 18, 2007, 06:28:32 AM

uf, it was there. just to see it :(
now, everything makes sense. ammonia was used to avoid competing ester hydrolysis....