1,4-addition of enolates to enones (“The Michael Reaction”)

by James


Enolates of carbonyl compounds will add to an α,β-unsaturated carbonyl compounds to give 1,5-dicarbonyl compounds. This is called the Michael reaction.


Enolates are excellent nucleophiles; although a second resonance form is present with the negative charge on oxygen, the resonance form with the negative charge on carbon tends to be more important for determining reactivity.


Notes: Note that in each case a carbon-carbon bond is being formed


Removal of a proton from the ketone with strong base (Step 1, arrows A and B) results in an enolate, which then performs a 1,4-addition on the α,β-unsaturated carbonyl compound (Step 2, arrows C and D), which is then protonated (Step 3, arrows E and F).


Sodium here isn’t specifically important, it just balances out the negative charge.


{ 5 comments… read them below or add one }

Daniel April 6, 2012 at 12:28 pm

Thanks for the numbering part James. It was driving me mad.
Plus, your tip of always making sure to count my Carbons really helps as well.


james April 8, 2012 at 3:52 pm

It makes a big difference! Mistakes are really easy to make.


Vicki April 10, 2014 at 2:01 pm

Thank you this is easy to follow. I actually understand what is going on.


Smriti April 22, 2014 at 12:32 am

Thanks for numbering and this makes so much more sense!!!


Fiona Liang April 23, 2014 at 11:25 pm

Hey James! Quick question:I read in Klein’s book that Michael donors have to be an enolate from a di-carbonyl compound (because it’s more stable and less reactive, etc) in order to be selective to strictly undergo 1,4-addition. Is steric hinderance the reason why 1,4-addition prefer to occur in this case?

Many thanks!


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