MPAThio Ligand-Accelerated Palladium-Catalyzed Nondirected Hydrogen Isotope Exchange of Arenes with D2O

Abstract

Hydrogen isotope exchange is an atom-economical strategy for accessing deuterium-labeled molecules, but its synthetic utility is often limited by slow exchange kinetics and poor reactivity of π-extended arenes. Herein, we report a palladium-catalyzed nondirected hydrogen isotope exchange (HIE) enabled by a dual-ligand combination of a monoprotected aminoethyl thioether (MPAThio) and an N-heteroarene ligand. This system exhibits faster HIE kinetics, reaching isotopic equilibrium within 30 min at 105 °C (and within 60 min at 90 °C), and enables efficient deuterium incorporation under mild conditions using D2O as the deuterium source. The protocol enables efficient deuteration of a broad range of mono- and multisubstituted arenes. For poorly soluble substrates relevant to organic light-emitting diode materials, a cosolvent strategy addresses solubility limitations, affording high deuterium incorporation. Mechanistic studies indicate that the MPAThio ligand lowers the barrier of accessing the reactive C–H activation manifold, thereby favoring efficient reversible HIE.