No abstract

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.

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.

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Efficient Palladium-Catalyzed Substitution in Enantiomerically PureAllyl Carbonates -A Stereodivergent Access to β-Aryl-Substituted γ-Lactones and γ-Hydroxy Amides.-Interestingly, the allylic substitution of the (E)-carbonate (I) proceeds with retention of configuration, whereas the substitution of the (Z)-carbonates (VI) occurs with inversion and Z/E isomerization yielding the diesters (VIII). π-σ-π Interconversions are responsible for these results. The diesters can easily be transformed into γ-lactones and γ-hydroxy amides. -(BRAUN, M.; UNGER, C.; OPDENBUSCH, K.; Eur.