A Diruthenium Catalyst for Selective, Intramolecular Allylic C–H Amination: Reaction Development and Mechanistic Insight Gained through Experiment and Theory

The mixed-valent paddlewheel complex tetrakis(2-oxypyridinato)diruthenium(II,III) chloride, [Ru2(hp)4Cl], catalyzes intramolecular allylic C–H amination with bis(homoallylic) sulfamate esters. These results stand in marked contrast to reactions performed with dirhodium catalysts, which favor aziridine products. The following discussion constitutes the first report of C–H amination using complexes such as [Ru2(hp)4Cl] and related diruthenium adducts. Computational and experimental studies implicate a mechanism for [Ru2(hp)4Cl]-promoted C–H amination involving hydrogen-atom abstraction/radical recombination and the intermediacy of a discrete, albeit short-lived, diradical species. The collective data offer a coherent model for understanding the preference of this catalyst to oxidize allylic (and benzylic) C–H bonds.