Co(III)‐Catalyzed [4+1] Annulation of Amides with Allenes via C−H Activation

A Co(III)‐catalyzed [4+1] annulation of amides with allenes to synthesize isoindolone and 1,5‐dihydro‐pyrrol‐2‐one derivatives is reported. A wide range of aromatic and vinylic amides react with allenes to give the corresponding annulation products in good to excellent yields. The mechanistic studies strongly support that the catalytic reaction proceeds through an amide‐directed C−H activation, followed by carbocobaltation of allene, β‐hydride elimination, and an intramolecular 1,2‐hydroamination.