Conjugate Additions of Enolate Ions Michael Addition and Robinson Annulation

CONJUGATE ADDITIONS OF ENOLATE IONS MICHAEL ADDITION AND ROBINSON ANNULATION 

Like other nucleophiles, enolate ions undergo conjugate additions to a,j3-unsaturated aldehydes and ketones, in a reaction known as the Michael addition. 

In this example, conditions have been chosen to favor formation of the thermodynamic enolate, the one with partial negative charge on the more highly substituted a-carbon (red recall Section 18-1). 

The mechanism of the Michael addition includes nucleophilic attack by the enolate ion on the j8-carbon of the unsaturated carbonyl compound (the Michael acceptor ), followed by protonation of the resulting enolate. 

As the mechanism indicates, the reaction works because of the nucleophilic potential of the a-carbon of an enolate and the electrophilic reactivity of the jS-carbon of an a,jS-unsaturated carbonyl compound. 

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