Palladium-Catalyzed Enantioselective Synthesis of Chiral Vinylallenes via γ-Selective Coupling of Vinylboronates with Propargylic Carbonates

We report a palladium/phosphoramidite-catalyzed asymmetric γ-selective cross-coupling of racemic propargylic carbonates with alkenyl boronates for the synthesis of axially chiral vinylallenes. This transformation provides a direct and modular entry to densely substituted vinylallenes under mild conditions, furnishing the desired products in good to excellent yields and high enantioselectivities (up to 91% yield and 95% ee). A broad range of propargylic carbonates and cyclic, styrenyl, and functionalized alkenyl boronates are well tolerated. The synthetic utility of the method is demonstrated by a mmol-scale reaction and downstream transformations of the vinylallene products.