15.37 : Koniugatowa addycja enolanów: addycja Michaela

Recall conjugate addition in an α,β-unsaturated carbonyl compound where the nucleophile adds to the β carbon of the C=C bond.

Michael addition is a type of conjugate addition involving nucleophiles containing activated methylene flanked by electron-withdrawing groups.

The reaction is catalyzed by a base that deprotonates the acidic methylene proton. This generates a doubly-stabilized enolate ion that serves as the nucleophile or the Michael donor on account of its lone pair.

Compounds comprising a methylene group with two adjoining electron-withdrawing substituents are effective Michael donors compared to normal enolates with a single electron-withdrawing neighbor.

The enolate attacks the β carbon of the α,β-unsaturated carbonyl compound. This conjugated system acts as the electrophile or the Michael acceptor.

The resulting compound has a new C–C σ bond, which, upon subsequent protonation, gives the Michael-addition product.