Cross-coupling of Aryl Sulfides Powered by N-Heterocyclic Carbene Ligands

Cross-coupling reactions of aryl sulfides are more difficult than they look. We have disclosed that transition metal-NHC complexes allow us to efficiently use a wide range of aryl sulfides as electrophilic coupling partners in various cross-coupling reactions and have thus significantly expanded the scope of aryl sulfides available for the cross-coupling technology. Newly introduced nucleophilic partners include arylzinc reagents, Grignard reagents such as alkynylmagnesium species, amines, ketimines, and diborons to achieve Negishi-type coupling, Kumada-Tamao-Corriu-type coupling, Buchwald-Hartwig-type amination, Buchwald-Hartwig-Miura-type carbonyl alpha-arylation, and Miyaura-type borylation, respectively. These cross-coupling reactions are particularly advantageous when combined with sulfur-specific transformations to prepare organosulfur substrates. Through the development of catalytic transformations of C-S bonds, sulfur based organic synthesis has come to complement conventional halogen-based organic methodology.