Cobalt‐Catalyzed Tandem C−H Activation/C−C Cleavage/C−H Cyclization of Aromatic Amides with Alkylidenecyclopropanes

A cobalt‐catalyzed chelation‐assisted tandem C−H activation/C−C cleavage/C−H cyclization of aromatic amides with alkylidenecyclopropanes is reported. This process allows the sequential formation of two C−C bonds, which is in sharp contrast to previous reports on using rhodium catalysts for the formation of C−N bonds. Here the inexpensive catalyst system exhibits good functional‐group compatibility and relatively broad substrate scope. The desired products can be easily transformed into polycyclic lactones with m ‐CPBA. Mechanistic studies revealed that the tandem reaction proceeds through a C−H cobaltation, β‐carbon elimination, and intramolecular C−H cobaltation sequence.