Palladium‐Catalyzed Cross‐Coupling of Alkenyl Carboxylates
Joseph Becica, Oliver R. J. Heath, Cameron H. M. Zheng, David C. Leitch
Abstract
Abstract 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 β‐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.