Hydrogen-Isotope Exchange (HIE) Reactions of Secondary and Tertiary Sulfonamides and Sulfonylureas with Iridium(I) Catalysts

For the first time we report the optimized hydrogenisotope exchange (HIE) conditions for the selective aromatic deuteriation of various sulfonylureas and tertiary sulfonamides, as well as for a broad range of secondary sulfonamides. Based on a comprehensive screening of readily available Ir catalysts, the Kerr-type NHC catalyst 5 proved to be most efficient in the HIE reaction of secondary sulfonamides and sulfonylureas. However, for tertiary sulfonamides, the commercially available Burgess catalyst 6, not yet utilized in HIE reactions, resulted in a much higher incorporation of deuterium. Finally, we tested the new HIE protocol for the labelling of a series of sulfa drugs and adapted the conditions to allow for selective tritium labelling.