The Robinson Annulation is a C–C bondforming reaction for the synthesis of sixmembered rings. It combines a Michael addition followed by an Aldol condensation. It is used in organic chemistry for ring formation to create 6 membered rings. For example, the reaction of a ketone such as cyclohexanone with an α,βunsaturated ketone such as methyl vinyl ketone to give the corresponding bicyclic enone.

General features:
1. It can be both acid and basecatalyzed.
2. It is a onepot reaction; however, higher yields are usually obtained when the Michael adduct is isolated and then subjected to the aldol reaction.

Reaction mechanism:
The mechanism involves the Michael addition of the enolate across the double bond of the α,βunsaturated ketone to produce the Michael adduct (a 1,5diketone). Then, the intramolecular Aldol reaction yields a cyclic βhydroxy ketone that is immediately dehydrated.

Pinterest:
https://www.pinterest.es/pin/67166973...

References:
https://nrochemistry.com/robinsonann...

Seminal publication:
J. Chem. Soc., 1935, 12851288. https://doi.org/10.1039/JR9350001285

Similar reactions:
Aldol reaction. Aldol condensation:    • Aldol Addition and Condensation  
Michael Addition reaction:    • Michael Addition  
Claisen Condensation:    • Claisen Condensation  
HajosParrish reaction (the enantioselective version of the Robinson Annulation)