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Topic: Rearrangement to conjugation  (Read 2282 times)

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Offline AlphaScent

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Rearrangement to conjugation
« on: July 05, 2017, 06:02:19 PM »
I submitted 4-methylsnisole to Birch conditions and then hydrolyzed the resulting enol-ether with PTSA and THF to give 4-methylcyclohex-3-en-1-one.  I expected hydrolysis to proceed to give the alpha, beta - unsaturated ketone.  It did not.  Upon reflux, it gave a mixture of products.  Mineral acid in water also gave a mixture of products.

Has anyone done this type of reaction with good results? 

Thanks in advance

P.S.: scifinder and reaxys were not much help
If you're not part of the solution, then you're part of the precipitate

Offline pgk

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Re: Rearrangement to conjugation
« Reply #1 on: July 06, 2017, 09:07:22 AM »
After neutralization of the ketones mixture, you heat it in presence of KOH or Et3N or DBU catalyst (DABCO), under nitrogen and you monitor by TLC. May be, you get something.
That way, I had have migrated exocyclic double bond to endocyclic ketone-conjugated one, in the past.
Hint 1: Nitrogen atmosphere is necessary because these compounds are easily oxidized to 4-methylphenol upon heating. Alternatively, you can add BHT up to 1% w/w to ketones mixture.
Hint 2: Avoid excessively high temperatures and/or long reaction times because aldol type, byproducts might be formed.
« Last Edit: July 06, 2017, 09:40:38 AM by pgk »

Offline TheUnassuming

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Re: Rearrangement to conjugation
« Reply #2 on: July 07, 2017, 05:54:00 PM »
Someone in our lab had some success clipping methyl enol ethers using Hg(TFA)2 or MgI2 systems.  Might be worth looking into, though I'm not sure what scale you need this reaction to work on.
Good luck!
When in doubt, avoid the Stille coupling.

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