Lactones, allylic reaction with sodium malonate

Activated methylene compounds such as dimethyl malonate have found substantial utility in palladium catalyzed allylic substitution reactions. Accordingly, the Krapcho decarboxylation is often used in conjunction with these reactions. As an example, the first total synthesis of enantiomerically pure (-)-wine lactone has utilized the sequence of reactions.27 First, the allylic substitution reaction of 2-cyclohexen-l-yl acetate (49) with alkali sodium dimethylmalonate yielded 51 with high enantioselectivity, as a result of the use of chiral phosphine ligand 50. The malonate was then subjected to Krapcho decarbomethoxylation using NaCl, H2O, and DMSO at 160 °C to yield 52. This reaction has been used similarly following the allylic substitution reaction with other malonate derivatives.28-30... 

Nncleophilic attack by carbanions on Pd rr-complexes provides an excellent method for carbon-carbon bond formation. The first example of natural product synthesis by the reaction of Pd rr-complex with carbon nucleophiles appears to be Holton s synthesis of prostanoids via treatment of an allylic amine with the stoichiometric amount of lithinm tetrachloropalladate and sodium diethyl malonate, followed by addition of diisopropy-lethylamine, which led to the formation of an isomerically pure bicyclic Pd-amine complex in 92% yield " (Scheme 18). The carbon nucleophile ends up a and trans to the dimethylamino group. Both regio- and stereochemistries must be controlled by the Me2N group. The amino diester intermediate was further transformed into Corey lactone diol, which had previously been converted to PGp2a in two steps and 80% overall yield. 

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