Illustrated Glossary of Organic Chemistry

Michael reaction (Michael addition): The conjugate addition of a carbanion, enolate, enamine, or other carbon nucleophile to the β-carbon of an enone, enal, or other α, β-unsaturated compound. This results in a new carbon-carbon bond at the β-carbon.The Michael reaction nucleophile is called the Michael donor. The Michael reaction electrophile is called the Michael acceptor.

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Piperidine

This Michael addition reaction begins with deprotonation of dimethyl malonate (red) with piperidine (a mild base) to form an enolate. This enolate (a nucleophile) then adds to the β-carbon of an α, β-unsaturated ketone (an enone and an electrophile; in blue). Note the new carbon-carbon bond (green, bold) formed at the β-carbon.

NaBH4 Pyridine

In this reaction, hydride (a nucleophile) adds to the β-carbon of an α, β-unsaturated ketone (an enone and an electrophile; in blue). This is a conjugate addition reaction, but not a Michael addition reaction, because the nucleophilic addition results in a new carbon-hydrogen bond (green bold), not a new carbon-carbon bond, at the β-carbon.