Selective deuteration of terminal olefins with D2O by catalysis of osmium-hydride complexes

Abstract

An efficient catalytic system for selective deuteration of terminal olefins using D₂O as the deuterium source has been developed. A series of osmium hydride complexes of the type OsHX(CO)(PR₃)₂(L) (where X represents halides) has been evaluated as catalyst precursors for H/D exchange between olefins and D₂O. The catalytic activity of the complexes was found to depend on the ligands present. Among the complexes tested, the OsHI(CO)(PPh₃)₃ complex exhibited excellent catalytic activity for the hydrogen–deuterium (H/D) exchange of terminal olefins with D₂O, especially in the presence of acetic acid. The system shows high selectivity for deuteration at terminal double bonds over internal ones. It can catalyze H/D exchange reactions of olefins without causing isomerization and can induce selective H/D exchange at the methine carbon (CHR) over the methylidene carbon (CH₂) for substrates RCHCH₂ with a bulky substituent R. Additionally, these reactions can be performed on substrates with various functional groups, making this system useful for selective labeling of olefins in complex molecules.