In three distinct steps, the Robinson annulation converts a ketone and an α,β-unsaturated ketone into a substituted cyclohexenone compound. First, the base creates an enolate ion intermediate, which reacts with the α,β-unsaturated ketone in a conjugate 1,4 addition (Michael reaction) to form a 1,5 diketone. An intramolecular aldol reaction occurs next, affording a cyclic β-hydroxy ketone. A final base-catalyzed dehydration affords the cyclohexenone product.

• Reagents: Base, Ethanol
• Reactant: Ketone, α,β-Unsaturated Ketone
• Product: Substituted Cyclohexenone
• Type of Reaction: Carbonyl Condensation Reaction (Michael and Intramolecular Aldol)
• Bond Formation: C-C (α-carbon of the ketone and the β-carbon of the unsaturated ketone) and C=C

Lab Tips

• This reaction can also be acid-catalyzed.
• Although a one-pot process is possible, yields tend to be higher when the Michael adduct is isolated and then subjected to the aldol reaction.
• The Michael reaction works best when a stable enolate ion adds to an unhindered α,β-unsaturated ketone.

Mechanism

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Related Reactions

Related Compounds