Cobalt-Catalyzed Switchable Intramolecular Thioenolization/C–H Thiolation and C(sp²)–H/C(sp³)–H Dehydrogenative Coupling

Abstract

Mild cobalt-catalyzed switchable regioselective and chemoselective thioenolization/C-H thiolation and C(sp²)-H/C(sp³)-H dehydrogenative couplings of <i>N</i>-aryl-<i>N</i>-alkyl-thioamides are developed, providing 2-methylene-2,3-dihydrobenzo[<i>d</i>]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(sp²)-H/C(sp³)-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.