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OR“The reaction of a ketone (most often a cyclic one) with an α,β-unsaturated ketone to give a substituted cyclohexenone derivative is known as the Robinson annulation.“
Features of the reaction:
Combination of three reactions: Michael addition, intramolecular aldol reaction, and dehydration.
Methyl vinyl ketone (MVK) and its various derivatives use as enone component; one-pot process, but yields tend to be higher when Michael adduct is isolated and then aldol reaction. Regioselective cyclization can also be achieved by using pre-formed enolates or enamines.
Mechanism:
Robinson annulation has three distinct steps: the Michael addition of the enol or enolate across the double bond of the α,β-unsaturated ketone to produce a 1,5-diketone (Michael adduct), followed by an intramolecular aldol reaction, which affords a cyclic β-hydroxy ketone (keto alcohol), and finally a base-catalyzed dehydration which gives rise to the substituted cyclohexenone.
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