Ruthenium-Catalyzed Deuteration of Alcohols with Deuterium Oxide

The catalytic properties of a series of ruthenium complexes for H/D exchange between D2O and alcohols were studied. The catalytic activity of the ruthenium complexes and the regioselectivity of the H/D exchange reactions were found to be dependent on the auxiliary ligands. While ruthenium η6-cymene complexes such as [(η6-cymene)RuCl(NH2CH2CH2NTs)]Cl, (η6-cymene)RuCl2/NH2CH2CH2OH, and (η6-cymene)Ru{(S,S)-NHCHPhCHPhNTs} catalyzed regioselective deuteration of alcohols with D2O at the β-carbon positions only, octahedral ruthenium complexes such as RuCl2(2-NH2CH2Py)(PPh3)2 (2-NH2CH2Py = 2-aminomethylpyridine) and RuCl2(NH2CH2CH2NH2)(PPh3)2 catalyzed regioselective H/D exchange reactions of D2O with alcohols at both the α- and β-carbon positions of alcohols. The H/D exchange reactions proceed through reversible dehydrogenation of alcohols and hydrogenation of carbonyl compounds involving hydride species and H/D exchange among D2O and carbonyl and hydride species. The different regioselectivities of the H/D exchange reactions can be related to the relative ease of H/D exchange of ruthenium hydride intermediates with D2O.