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Organic Chemistry Text Book (CHEM 3401 and 3402)

21.5.4a Michael Reaction

Conjugative addition of carbon nucleophiles to unsaturated esters, ketones, nitriles, sulfones and other activated double bonds is a useful synthetic method known as the Michael reaction. In combination with alkylations and condensations, the Michael reaction may be used to construct a wide variety of complex molecules from relatively simple starting materials. The carbon nucleophiles used in the following examples include cyanide ion, sodium diethylmalonate and the conjugate base of cyclohexane-1,3-dione. These anions are sufficiently stable that their addition reactions may be presumed reversible. If this is so, the thermodynamic argument used for hetero-nucleophile additions would apply here as well, and would indicate preferential formation of 1,4-addition products. Cyanide addition does not always follow this rule, and aldehydes often give 1,2-products (cyanohydrins). In each case the initial reaction is a Michael addition, and the new carbon-carbon bond is colored magenta. Any subsequent bonds that are formed by other reactions are colored orange.

In all the above examples the vinylagous electrophile (Michael acceptor) is drawn on the left, and the carbon nucleophile (Michael donor) is to its right. By clicking the "More Examples" button, four additional Michael reactions will be displayed. These illustrate the use of unsaturated nitrile and extended vinylagous acceptors, and enamine and nitroalkane donors.