[kriggy]

Hi,
is it possible to do two FC acylations on activated aromatic ring? For example on hydroquinone?
I tried to search a literature but no hits so far. Im not realy sure if its possible but our proffesor says that its all about conditions so..
Its for synthesis exercise so it could be "paper chamistr" but I would rather develop real way.


And I know that phenols can be carboxylated to form salycilic acid, is possible with hydroquinone into 2nd stage (ie dihydroxy terepthalic acid?) Since the 1st COOH is deactivating I doubt it but I might just ask as well if you didnt see it in literature. (no hits in literature search too)

[AromaticAcrobatic]

Why are you thinking this wouldn't be possible?

It seems like it would be all about the ratio of reagents to reactants..

[phth]

I asked a similar question to this on this forum a while ago.  It should work and you can improve the standard procedure.  Archer gave me a great answer and ill repeat it. It depends.  My case was a acylation followed by a alkylation to close a ring.  Conditions were 2 days DCM reflux for 35% desired pdt best time.  Solved this by adding an equivalent of nitromethane, and run at 0C.  Other lewis acid's could improve the yield, but nitrometane is an easy way to increase lewis acidity.  It forms 1:1 and 1:2 and 2:1 complexes.  Just add equivalent of it along with the LA cold addition, add to acyl chloride, then introduce the aromatic reagent.

[kriggy]

Why are you thinking this wouldn't be possible?

It seems like it would be all about the ratio of reagents to reactants..

Right, I somehow thought that you need activated system for acylation since the 1st acyl will deactivate the system.

phth thanks for suggestion
The other thing now is to figure out sequence of steps so all the substitutions go into the right positions

Anyway another question appeared in my mind:
Carbonyl group deactivates the aromatic ring. If I did umpolung on that carbonyl group with for example 1,3-propanedithiol, could it change the deactivating group into activating?

[AromaticAcrobatic]

Okay, remember that OH groups are the most activating and if you draw out the reaction you see that the OH groups takes care of the carbocation that is formed from the Acylations.

Also, you can acylate without an activating group, it would just take a little longer and/or require some assistance like heat perhaps.

 

[kriggy]

Thanks for pointing that out
I already have a way without the need of double FC acylation but It  might add more questions from me in the future about viability of reactions I used

[zsinger]

Possible, YES.....Clean, NO NO NO!!!!!  Separations of isomers will be VERY VERY challenging.
     Z