Site-Selective C-S Bond Formation at C-Br over C-OTf and C-Cl Enabled by an Air-Stable, Easily Recoverable, and Recyclable Palladium(I) Catalyst

This report widens the repertoire of emerging Pd-I catalysis to carbon-heteroatom, that is, C-S bond formation. While Pd-0-catalyzed protocols may suffer from the formation of poisonous sulfide-bound off-cycle intermediates and lack of selectivity, the mechanistically diverse Pd-I catalysis concept circumvents these challenges and allows for C-S bond formation (S-aryl and S-alkyl) of a wide range of aryl halides. Site-selective thiolations of C-Br sites in the presence of C-Cl and C-OTf were achieved in a general and a priori predictable fashion. Computational, spectroscopic, X-ray, and reactivity data support dinuclear Pd-I catalysis to be operative. Contrary to air-sensitive Pd-0, the active Pd-I species was easily recovered in the open atmosphere and subjected to multiple rounds of recycling.