Cooperative Catalytic Reactions Using Distinct Transition-Metal Catalysts: Ruthenium- and Copper-Catalyzed Enantioselective Propargylic Alkylation

The enantioselective propargylic alkylation of propargylic alcohols with beta-ketoesters in the presence of a thiolate-bridged diruthenium complex and a copper complex as co-catalyst affords the corresponding propargylic alkylated products in excellent yields as a mixture of two diastereoisomers with high enantioselectivity (up to 95?% enantiomeric excess (ee)). The findings reported herein not only open up a new type of enantioselective propargylic substitution reaction, but also a new aspect of cooperative catalytic reactions using distinct transition metals to realize a useful transformation that cannot be achieved by a single catalyst.