Illustrated Glossary of Organic Chemistry

Robinson annulation (Robinson annelation): An annulation (ring-forming) condensation reaction in which a ketone with at least one α-hydrogen is reacted with an α,β-unsaturated ketone. The reaction involves a Michael addition reaction followed by an aldol condensation reaction.

In this Robinson annulation reaction example, 2-methylcyclohexanone is reacted with methyl vinyl ketone in the presence of sodium ethoxide (NaOCH₂CH₃; a strong base) in ethanol (CH₃CH₂OH; a protic solvent) to give a bicyclic β-hydroxy ketone intermediate. This intermediate is then dehydrated to give the bicyclic enone product.