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.