Chelation-Assisted β-Selective Direct C-H Bond Arylation of 2-Thienylthioamide Catalyzed by Palladium-1,10-Phenanthroline Complexes

A palladium-1,10-phenanthroline-catalyzed chelation-assisted beta-selective direct C-H bond arylation of thienylthioamide was developed. The base used critically affected the reactivity: a beta-selective (3-selective) reaction took place with K2CO3, and both the alpha- and beta-positions were arylated to give 3,5-diarylated product with the use of Cs2CO3. The chelation-assisted palladation affording palladacycles was confirmed by stoichiometric reactions of thienylthioamide and the catalyst precursor.