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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: racemiz.er on August 02, 2022, 11:45:30 AM

Title: Imine-Enamine Tautomerism
Post by: racemiz.er on August 02, 2022, 11:45:30 AM
Okay, this is a tricky one... more of a thinker's question!

So, I was studying some imine formations. I was wondering if a tautomerism of imine is possible on the nitrogen end.

(https://i.ibb.co/y42BqQ9/tautomerism.png)

Any ideas guys?
Title: Re: Imine-Enamine Tautomerism
Post by: hollytara on August 02, 2022, 06:55:18 PM
Yes - imines can easily tautomerize. 

But the one you show it is disfavored - double bond better next to aromatic ring and double bond better if NOT exocyclic to cyclohexane.

Often an amine / carbonyl is used that forms an exocyclic double bond so as to favor isomerization to the endocyclic, which then reacts predictably. 
Title: Re: Imine-Enamine Tautomerism
Post by: rolnor on August 03, 2022, 01:23:43 AM
This is true for enamines, not imines. Enamines can form iminium salts. You need a secondary amine to get a enamine.
Title: Re: Imine-Enamine Tautomerism
Post by: racemiz.er on August 03, 2022, 02:24:33 AM
Yes - imines can easily tautomerize. 

But the one you show it is disfavored - double bond better next to aromatic ring and double bond better if NOT exocyclic to cyclohexane.

Often an amine / carbonyl is used that forms an exocyclic double bond so as to favor isomerization to the endocyclic, which then reacts predictably.

Ummm... basically the cyclohexyl amine is a part of a cis isomeric cyclohexane ring. Do you have any suggestions for making it trans? Basically i am trying to invert cis 1,4 substituted cylohexane to trans 1,4 substituted cyclohexane
Title: Re: Imine-Enamine Tautomerism
Post by: rolnor on August 03, 2022, 05:16:30 PM
You dont get the double bond on the cyclohexane, thats wrong. What substituents do you have on the ring? Its probably no problem to invert.
Title: Re: Imine-Enamine Tautomerism
Post by: racemiz.er on August 04, 2022, 01:20:17 AM
You dont get the double bond on the cyclohexane, thats wrong. What substituents do you have on the ring? Its probably no problem to invert.

Hydroxy on para position. Unsure on how to invert. Is there a chemical process for inversion (not substitution)?
Title: Re: Imine-Enamine Tautomerism
Post by: kriggy on August 04, 2022, 02:55:29 AM
Mitsunobu is usually used for this. react it with acetic acid and then hydrolyze the ester and you get inversion
Title: Re: Imine-Enamine Tautomerism
Post by: rolnor on August 04, 2022, 06:04:44 AM
And that is substitution!