BARBIER-TYPE REACTIONS OF CYCLIC ACID ANHYDRIDES AND KETO ACIDS MEDIATED BY AN SMI2 (NII2-CATALYTIC) SYSTEM - PREPARATION OF DISUBSTITUTED LACTONES/

Cyclic acid anhydrides (succinic and glutaric anhydrides and some of t heir derivatives) undergo fast Barbier-type reactions mediated by sama rium 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 iodi des can be used. In these reactions the formation of a samarium keto c arboxylate intermediate is likely; as a matter of fact. keto carboxyli c acids react under similar conditions to also yield disubstituted lac tones. It is demonstrated that lactonisation occurs during hydrolysis of the reaction.