Cobalt-Catalyzed Switchable Intramolecular Thioenolization/C-H Thiolation and C(sp)-H/C(sp)-H Dehydrogenative Coupling.

Mild cobalt-catalyzed switchable regioselective and chemoselective thioenolization/C-H thiolation and C(sp)-H/C(sp)-H dehydrogenative couplings of -aryl--alkyl-thioamides are developed, providing 2-methylene-2,3-dihydrobenzo[]thiazoles and thio-oxindoles in moderate to excellent yields from the same precursors, respectively. Details mechanistic studies suggest that the thioenolization/C-H thiolation process involves a radical mechanism, whereas the C(sp)-H/C(sp)-H dehydrogenative coupling might proceed through an electrophilic cobaltation(III) pathway. Thus, the selectivity for either product is achieved by accessing unique catalytic cycles involving different valence states for cobalt.