Palladium-Catalyzed Enantioselective Cyclization of 1,6-Enynes through Intramolecular Chlorine Transfer as a Novel Strategy for Asymmetric Halopalladation.

ABSTRACT

Palladium-catalyzed enantioselective cyclization of enynes has contributed significantly to the construction of chiral cyclic molecules. In contrast, the catalytic asymmetric cyclization involving halopalladation remains an unresolved challenge with the inevitable disturbance of the halide ions. Herein, an intramolecular chlorine transfer strategy is used to accomplish the enantioselective chloropalladation cyclization of 1,6-enynes. This reaction provides a redox-neutral approach to a variety of chiral α-chloromethylene-γ-butyrolactones with excellent E selectivity and enantioselectivity. The precisely controlled coordination of palladium with both the in situ generated nucleophilic species and the monodentate phosphoramidite ligand is crucial for enantioselectivity.