Enantioselective Vinylogous Addition of Enones to Allenes Enabled by Synergistic Borane/Palladium Catalysis

Herein, we report a method for enantioselective vinylogous addition of enones to alkoxyallenes enabled by synergistic borane/palladium catalysis. The inductive effect provided by borane coordination to the ketone was essential for closing the gap between the conditions needed for the generation of a dienolate and those needed for initiation of the palladium catalytic cycle by protonation of the metal catalyst. Furthermore, we accomplished the first example of stereodivergent synthesis with chiral borane/transition-metal catalysts.