Multiple Site Hydrogen Isotope Labelling of Pharmaceuticals.

Radiolabelling is fundamental in drug discovery and development as it is mandatory for preclinical ADME studies and late‐stage human clinical trials. Herein, a general, effective, and easy to implement method for the multiple site incorporation of deuterium and tritium atoms using the commercially available and air‐stable iridium precatalyst [Ir(COD)(OMe)]2 is described. A large scope of pharmaceutically relevant substructures can be labelled using this method including pyridine, pyrazine, indole, carbazole, aniline, oxa‐/thia‐zoles, thiophene, but also electron‐rich phenyl groups. The high functional group tolerance of the reaction is highlighted by the labelling of a wide range of complex pharmaceuticals, containing notably halogen or sulfur atoms and nitrile groups. The multiple site hydrogen isotope incorporation has been explained by the in situ formation of complementary catalytically active species: monometallic iridium complexes and iridium nanoparticles. [ABSTRACT FROM AUTHOR]