Efficient Palladium-Catalyzed Substitution in Enantiomerically Pure Allyl Carbonates – A Stereodivergent Access to β-Aryl-Substituted γ-Lactones and γ-Hydroxy Amides

Allyl carbonates (Z)-8 and (E)-9 are available from the addition of the chiral alkenyllithium reagent 5b to aromatic aldehydes 6. When sujected to a palladium-catalyzed substitution by sodium malonate, (Z)-carbonates 8 give diesters 10 and 11, whereas (E)-carbonate 9 predominantly leads to the diastereomeric product 12. The latter is converted into (S)-γ-butyrolactone 13 in a three step sequence. When the same protocol is applied to the isomeric diesters 10 and 11, (R)-lactones 13 result. A rationale for the stereochemical outcome of the allylic substitutions in the carbonates 10-12 is offered, based on π-σ-π interconversions of the palladium complexes 20-23.