Redox‐Neutral Rhodium‐Catalyzed [4+1] Annulation through Formal Dehydrogenative Vinylidene Insertion

A synthetic protocol for the expedient construction of 5‐methylene‐1H‐pyrrol‐2(5H)‐one derivatives through rhodium‐catalyzed [4+1] annulation with gem‐difluoroacrylate as the C1 component was reported. By taking advantage of the twofold C−F bond cleavage occurring during the annulation, this reaction not only allows the synthesis of these heterocyclic compounds under overall oxidant‐free conditions but also renders the transformation stereospecific. The very mild reaction conditions employed ensure compatibility with a wide variety of synthetically useful functional groups. Oxidant‐free: Rhodium‐catalyzed [4+1] annulation of amide and gem‐difluoroacrylate is developed. By taking advantage of the twofold C−F bond cleavage, this reaction not only allows the synthesis of 5‐methylene‐1H‐pyrrol‐2(5H)‐one and 3‐methyleneisoindolin‐1‐one derivatives under overall oxidant‐free conditions but also most importantly renders the transformation stereospecific.