Water as a Hydride Source in Palladium‐Catalyzed Enantioselective Reductive Heck Reactions

Pd‐catalyzed intramolecular asymmetric carbopalladation of N ‐aryl acrylamides followed by reduction of C(sp³)‐Pd intermediate using diboron–water as a hydride source afforded enantioenriched 3,3‐disubstituted oxindoles in high yields and enantioselectivities. When heavy water was used as a deuterium donor in combination with bis(catecholato)diboron (Cat₂B₂), deuterium was incorporated into the products with high synthetic efficiency. The ligand determined both the enantioselectivity of the reaction and the reaction pathways, thereby affording either hydroarylation (reductive Heck) or carboborylation products.