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. The participation of non-strained structures generally relies on cleavage of a polar carbon–CN bond or assistance of a directing group.

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. Experimental and computational studies show that the initially formed tetrahedral dicobalt-alkyne complex undergoes C1-C2 activation via oxidative addition with Co(0), followed by migratory insertion and reductive elimination to give the -naphthol products.