Direct C-H Bond Arylation of Thienyl Thioamides Catalyzed by Pd-Phenanthroline Complexes.

A direct C-H bond arylation method for thienyl thioamides catalyzed by [Pd(phen)2](PF6)2 was developed. This reaction selectively afforded 2-monoarylated products, while the corresponding amide thiophene derivatives furnished 2,5-diarylated products. Mechanistic studies revealed that a Pd(II)-bisthioamide complex should be the active species for the reaction of thienyl thioamides in the presence of catalytic amounts of [Pd(phen)2](PF6)2. Similar to the reaction with amides, the reaction with thioamides selectively generated the 2,5-diarylated products when a preformed Pd(phen)PhI complex was used.