Cerium(III) Chloride Catalyzed Michael Reaction of 1,3-Dicarbonyl Compounds and Enones in the Presence of Sodium Iodide Under Solvent-Free Conditions

Cerium(III) chloride heptahydrate in the presence of sodium iodide catalyses the Michael addition of 1,3-dicarbonyl compounds to α,β- unsaturated ketones and α,β-unsaturated aldehydes with extraordinary efficiency. The very mild conditions allow high chemoselectivity as shown by the absence of the typical side reactions, which can be observed in the conventional base-catalyzed processes. More interestingly, when at least one of the starting materials is liquid at room temperature, the reaction can also be performed without solvents. The CeCl3 · 7 H2O/NaI catalyst system can be easily separated from the reaction mixture and it can be reused without an appreciable loss of activity. Advantages of the present procedure, which utilizes cheap and 'friendly' reagents, over the previously reported ones, are discussed.