Cobalt-Catalyzed Intramolecular Alkyne/Benzocyclobutenone Coupling: C-C Bond Cleavage via a Tetrahedral Dicobalt Intermediate.

A Co(0)-catalyzed intramolecular alkyne/benzocyclobutenone coupling through C-C cleavage of benzocyclobutenones is described. Co(CO)/P[3, 5-(CF)CH] was discovered to be an effective metal/ligand combination, which exhibits complementary catalytic activity to the previously established rhodium catalyst. In particular, the C8-substituted substrates failed in the Rh system, but succeeded with the Co catalysis.

"Cut and Sew" Transformations via Transition-Metal-Catalyzed Carbon-Carbon Bond Activation.

The transition metal-catalyzed "cut and sew" transformation has recently emerged as a useful strategy for preparing complex molecular structures. After oxidative addition of a transition metal into a carbon-carbon bond, the resulting two carbon termini can be both functionalized in one step via the following migratory insertion and reductive elimination with unsaturated units, such as alkenes, alkynes, allenes, CO and polar multiple bonds. Three- or four-membered rings are often employed as reaction partners due to their high ring strains.