Cobalt-Catalyzed, Hydroxyl-Assisted C-H Bond Functionalization: Access to Diversely Substituted Polycyclic Pyrans.

Highly efficient oxidative annulation of alkynes furnished diversely substituted pyran[2,3,4- de]chromene-2-one derivatives and related polycycles in moderate to high yield. The reaction is catalyzed by nontoxic, air-stable, and inexpensive Cp*Co(CO)I2 catalyst. The hydroxyl moiety at the substrate acts as the directing group for the C-H bond activation.