Rhodium(I)-Catalyzed Formate-Mediated Domino Heck/1,4-Hydride Addition toward Oxindoles

We report a rhodium-catalyzed domino strategy for the preparation of oxindole-containing products starting from simple ortho-bromoaniline-derived acrylamides. Mechanistic and computational studies demonstrate that the reaction initially proceeds through a Heck-type process to generate the benzylidene intermediate via a β-hydride elimination. Subsequently, a RhI–hydride species is generated in situ and forms the final oxindole products through a 1,4-conjugate addition of the hydride. Key to success is the use of sodium formate as it enables the generation of the rhodium hydride species, as well as allowing for the catalyst turnover.