Carboxylate esters have many desirable features as electrophiles for catalytic cross-coupling: they are easy to access, robust during multistep synthesis, and mass-efficient in coupling reactions. Alkenyl carboxylates, a class of readily prepared non-aromatic electrophiles, remain difficult to functionalize through cross-coupling. We demonstrate that Pd catalysis is effective for coupling electron-deficient alkenyl carboxylates with arylboronic acids in the absence of base or oxidants. Furthermore, these reactions can proceed by two distinct mechanisms for C-O bond activation. A Pd(0/II)catalytic cycle is viable when using a Pd(0)precatalyst, with turnover-limiting C-O oxidative addition; however, an alternative pathway that involves alkene carbopalladation and beta-carboxyl elimination is proposed for Pd(II)precatalysts. This work provides a clear path toward engaging myriad oxygen-based electrophiles in Pd-catalyzed cross-coupling.
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