Barbier-Type Reactions of Cyclic Acid Anhydrides and Keto Acids Mediated by an SmI2-(NiI2-Catalytic) System – Preparation of Disubstituted Lactones

Abstract

Cyclic acid anhydrides (succinic and glutaric anhydrides and some of their derivatives) undergo fast Barbier-type reactions mediated by samarium diiodide in the presence of catalytic amounts of nickel diiodide (1 mol-% with respect to SmI2), to give disubstituted lactones in high yields. Without NiI2 no reaction occurs. Various alkyl and allyl iodides can be used. In these reactions the formation of a samarium keto carboxylate intermediate is likely; as a matter of fact, keto carboxylic acids react under similar conditions to also yield disubstituted lactones. It is demonstrated that lactonisation occurs during hydrolysis of the reaction.